HS-PS4-4: Evaluating Claims About Electromagnetic Radiation and Living Tissue
In plain English: HS-PS4-4 is the NGSS high school performance expectation that asks students to judge whether published claims about electromagnetic radiation absorbed by matter are valid and reliable. The key idea is that higher-frequency photons carry more energy, so ultraviolet, X-rays and gamma rays can damage living tissue in ways radio waves cannot. It is usually taught in Physics or Physical Science.
Evaluate the validity and reliability of claims in published materials of the effects that different frequencies of electromagnetic radiation have when absorbed by matter.
Clarification Statement: Emphasis is on the idea that different frequencies of light have different energies, and the damage to living tissue from electromagnetic radiation depends on the energy of the radiation. Examples of published materials could include trade books, magazines, web resources, videos, and other passages that may reflect bias.
Assessment Boundary: Assessment is limited to qualitative descriptions.
Next Generation Science Standards · Disciplinary Core Idea: Waves and Their Applications in Technologies for Information Transfer · Official standard
Students read short invented excerpts written in the style of trade books, magazines, websites, videos and advertisements, and decide two things about each claim. Is it valid, meaning consistent with what physics says happens when radiation of that frequency is absorbed? Is it reliable, meaning backed by a trustworthy source and evidence that others can check? The science behind every verdict is one idea: the energy carried by each photon rises with frequency, so radio waves, microwaves and infrared mainly warm matter, visible and ultraviolet light can change single molecules, and the highest-energy ultraviolet, X-rays and gamma rays can ionize atoms and break DNA.
The NGSS Clarification Statement says: "Emphasis is on the idea that different frequencies of light have different energies, and the damage to living tissue from electromagnetic radiation depends on the energy of the radiation. Examples of published materials could include trade books, magazines, web resources, videos, and other passages that may reflect bias." The Assessment Boundary says: "Assessment is limited to qualitative descriptions." So every question on this page asks for a qualitative description or judgment, and students never have to calculate a photon energy. All excerpts, product names and data sets are invented for teaching. Students do the practice of obtaining, evaluating and communicating information: they annotate claims, rate sources, test a product claim with UV beads and write their own fact-check.
Learning Objectives
By the end of this lesson, students will be able to:
Order the bands of the electromagnetic spectrum by frequency and describe how the energy of each photon changes along the spectrum
Describe qualitatively what happens when radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays are absorbed by living tissue
Judge the validity of a published claim by comparing it with the physics of photon energy, intensity and exposure time
Judge the reliability of a source by its expertise, cited evidence, independent confirmation and possible bias
Write a short evaluation that states a verdict on validity and reliability and names the evidence behind it
Prior Knowledge Required
Students should already be comfortable with:
Waves being reflected, absorbed or transmitted by materials MS-PS4-2
The relationship among frequency, wavelength and wave speed HS-PS4-1
Light described as a stream of photons as well as a wave HS-PS4-3
Telling a claim from the evidence offered for it in a science text
Project four everyday sources without any headings: a car radio playing, a heat lamp over a buffet, an afternoon at the beach, a dental X-ray.
Warm-Up Prompt
"Rank these four from most to least likely to damage the DNA in your skin cells. Then write what your ranking is based on: brightness, warmth, how long you are exposed, or something else?"
Collect rankings on the board. Many students rank the heat lamp high because it feels hot, or rank the radio high because it is on all day. Keep the list: at the end of the lesson students revisit it with the idea of energy per photon.
Direct Instruction15-20 minutes
Photon energy. All electromagnetic radiation travels at the same speed in a vacuum, but it arrives in packets (photons) whose energy is proportional to frequency (E = hf, where h is Planck's constant). Use Diagram 1. Going from radio to gamma rays, the frequency and the energy of each photon rise by a huge factor. Brightness, or intensity, tells how many photons arrive each second, not how much energy each one carries.
What absorption does. When tissue absorbs radio waves, microwaves or infrared, the energy mainly makes molecules move faster, so the tissue warms; any harm needs a high intensity for long enough to heat it. A single visible or ultraviolet photon can change one molecule: visible light drives vision and photosynthesis, and ultraviolet can rearrange bonds in DNA. Photons above about 10 electron volts, from the highest-energy ultraviolet through X-rays and gamma rays, can knock electrons out of atoms (ionize them) and break DNA strands. For ionizing radiation, even a low intensity delivers some damaging photons, so the total dose matters.
Two separate questions. Validity asks whether the claim agrees with this physics and with the evidence. Reliability asks whether the source can be trusted: who wrote it, whether evidence is cited and checkable, whether independent groups got the same result, and whether the author gains from the claim. Use Diagram 2 as the checklist for the examples below. All five excerpts are invented.
Web resource from a seller
A website that sells "shielding pendants" states: "Wi-Fi routers give off radiation that breaks your DNA the same way X-rays do." No sources are cited.
Result: Invalid: Wi-Fi uses radio waves (2.4 and 5 GHz) whose photons carry hundreds of thousands of times too little energy to ionize atoms, so they cannot break DNA as X-rays do. Unreliable: the author profits from the fear and offers no evidence.
Trade book by a dermatologist
A popular book on skin health, written by a practicing dermatologist and citing medical studies, says: "The UV-B in sunlight can alter the DNA in skin cells directly, which is one reason repeated sunburns raise the risk of skin cancer."
Result: Valid: UV-B photons carry more energy than any visible photon, enough to rearrange bonds in DNA even though they are not ionizing. Reliable: an expert author who cites evidence others can check.
Video from a cooking channel
A popular video claims: "Microwave ovens blast food with radiation that destroys its molecules and leaves it radioactive." The host gives no sources.
Result: Invalid: microwaves (2.45 GHz) make water molecules rotate and jostle their neighbors, so the food heats up. The photons cannot ionize atoms, and nothing changes the nuclei, so the food cannot become radioactive. Unreliable: entertainment source, no evidence.
Magazine advertisement (may reflect bias)
A full-page ad for a tanning salon in a lifestyle magazine says: "Our beds use mostly UV-A, the gentle rays that tan without burning, so a base tan is a safe way to protect your skin."
Result: Invalid: UV-A photons carry less energy than UV-B but still more than visible light; UV-A reaches deeper into the skin and damages DNA indirectly, and health agencies classify tanning beds as a cause of cancer. Biased: the salon sells tanning sessions.
Government health agency web page
A national health agency page, reviewed by radiologists and dated, explains: "Dental X-rays are ionizing, so the beam is narrowed and aimed only at the teeth being imaged, and images are taken only when the dentist needs them."
Result: Valid: X-ray photons (tens of thousands of electron volts) can ionize atoms in any tissue they are absorbed by, so limiting which tissue the beam reaches, and how often, makes sense. Reliable: expert reviewers, no product to sell, and the page can be checked against other agencies.
After each example ask two questions in order: "What does the physics say?" (validity) and "Why should we believe this source?" (reliability). Point out that a claim can be valid but poorly sourced, or come from a respected source and still be overstated.
Guided Practice15-20 minutes
Pairs read the invented blog post below, then fill in the table one sentence at a time. Model the first row aloud.
"Screens Are Blinding Our Kids" (invented post on the blog of a company that sells blue-light glasses): "Blue light is the highest-energy visible light, so hours of screen time burn the retina the way the sun burns skin. Every child needs our glasses. Eye doctors don't want you to know this."
Guided practice: annotating the blue-light post (teacher key)
Sentence
Consistent with physics?
Evidence given?
Signs of bias?
Blue light is the highest-energy visible light
Mostly: blue and violet sit at the high-frequency end of the visible range, so their photons carry the most energy of any visible light
None needed; checkable in any physics text
No
Screen time burns the retina the way the sun burns skin
Not supported: blue photons carry less energy than UV, and a screen is far dimmer than daylight
None
Exaggeration
Every child needs our glasses
Not a physics claim
None
Yes: the author sells the glasses
Eye doctors don't want you to know this
Not a physics claim
None
Yes: appeal to a hidden secret instead of evidence
Separate the one sentence that is sound physics from the sentences that go beyond it.
Decide what evidence would be needed to support the retina claim (for example, eye measurements from independent researchers).
Write a two-sentence verdict: one on validity, one on reliability.
Independent Practice10-15 minutes
Each student evaluates an invented online product listing for a handheld UV-C wand: "Kills 99.9% of germs in 10 seconds! Uses the same UV-C light hospitals use. Safe for hands, face and pets: just wave it over your skin after shopping."
Students write a paragraph that answers: Which part of the claim is consistent with the physics of UV-C? Which part is not, and why? What would make the 99.9% figure reliable? Key points: UV-C photons carry even more energy than UV-B, so UV-C can damage the DNA and RNA of microbes, which is why it is used to disinfect surfaces and air. The same photons also damage skin and eye cells, so "safe for skin and face" is invalid. The 99.9% figure gives no test conditions, no distance or exposure time, and no independent lab.
Closure5 minutes
Exit ticket: "Name one kind of radiation that mainly heats tissue when absorbed and one that can ionize atoms. Then write one question you would ask about the source of any health claim." Return to the warm-up rankings and ask students to re-rank the four sources using energy per photon and exposure, and to explain which ranking changed.
Differentiation Strategies
For Struggling Students
Give a printed copy of Diagram 1 and have students place each claim's radiation on it before judging validity
Provide a sentence frame: "This claim is valid / not valid because ___ photons carry ___ energy. The source is / is not reliable because ___."
Start with two-sentence excerpts that contain one physics claim each before moving to longer passages
For Advanced Students
Have students find a real published claim about radiation, identify its original source, and trace whether the claim changed as it was repeated
Ask students to explain why the risk from ionizing radiation is described by dose and probability, while the risk from microwaves is described by heating
Ask students to rewrite an invalid excerpt so that it is valid while keeping as much of the original message as possible
Assessment Guidance
What to Look For
Check that students judge validity by the energy of each photon and not by brightness, warmth or the word "radiation". Look for evaluations that keep validity and reliability separate and give a reason for each. Listen for students who treat all radiation as equally dangerous, who think anything exposed to radiation becomes radioactive, or who trust a claim because it is popular or has a professional-looking website.
02
Classroom Activities
3 Activities
1
Claim Card Stations
20 minGroups of 3-4
Six stations each hold one invented excerpt. At each station groups place the radiation on Diagram 1, then rate the claim on validity (valid, partly valid, invalid) and the source on reliability (reliable, mixed, unreliable), giving one reason for each rating. Groups rotate every 3 minutes.
Station Cards
Card 1, trade book by a university physicist: "You can see because a single photon of visible light can change the shape of one pigment molecule in your eye. That is a chemical change, not heating."
Card 2, lifestyle magazine article: "Sitting by a sunny office window can't cause sun damage, because glass blocks all ultraviolet light."
Card 3, web page of a company that sells grounding mats: "Sleep on our mat to drain the radiation your body soaks up from TV screens. Tested by our engineers."
Card 4, hospital video with a medical physicist: "A CT scan gives a much larger X-ray dose than a single chest X-ray, so doctors order one only when the information is worth the added risk."
Card 5, sponsored newsletter from a lamp company: "Our lamp's gentle ultraviolet glow boosts your immune system with zero risk. Leave it on all night."
Card 6, anonymous forum post: "Black lights at parties give off the same radiation as X-ray machines."
Teacher Key
Cards 1 and 4 are valid and come from reliable sources. Card 2 is partly valid: ordinary window glass blocks most UV-B but lets much of the UV-A through, so "all ultraviolet" is wrong, although the magazine is a mixed source. Cards 3, 5 and 6 are invalid and unreliable: light from a screen that the body absorbs becomes a tiny amount of thermal energy, so there is no stored radiation to drain; ultraviolet can damage skin and eyes; and black lights give off UV-A, whose photons are far too low in energy to ionize atoms as X-rays do.
Discussion Questions
Two of the six cards are both valid and reliable. What do their sources have in common?
Card 2 mixes a true fact with an overstatement. Which word makes it invalid, and how would you fix it?
Cards 3 and 5 both come from sellers. Could a seller ever publish a valid claim? What would you need to trust it?
Modification for Distance Learning
Post each card as a slide. Students record their ratings and reasons in a shared form, and the class compares the spread of ratings for each card before discussing the key.
2
UV Bead Test of Product Claims
25 minPairs
UV-sensitive beads stay white under ordinary indoor light and turn purple when ultraviolet photons are absorbed by a dye in the bead. Pairs use them to test three product claims: "clear plastic wrap lets UV through", "SPF 30 sunscreen blocks UV" and "any dark lens protects your eyes from UV".
Procedure
Thread 10 beads on each of six pipe cleaners. Keep them in a closed envelope until they are all white.
Prepare six conditions: indoors under the LED ceiling lights; direct sunlight uncovered; sunlight under clean plastic wrap; sunlight under plastic wrap with a thin, even layer of SPF 30 sunscreen; sunlight under a lens labeled UV400; sunlight under a tinted lens with no UV label.
Expose all six at the same time for 60 seconds, then score the color of each set from 0 (white) to 4 (dark purple) against a color card.
Safety: never look at the sun, even through a lens. Wear gloves to spread sunscreen and wash hands afterward. If you use a UV-A flashlight instead of sunlight, point it only at the beads and never at anyone's eyes. Do not use UV-C lamps.
Sample Data (invented)
Color scores after 60 s: indoors under LED lights 0; open sunlight 4; under plastic wrap 4; plastic wrap with SPF 30 sunscreen 1; UV400 lens 0; tinted lens with no UV label 3.
Discussion Questions
Why did the beads stay white under bright LED lights but turn dark in sunlight? Use the energy of each photon in your answer.
Why is the plastic-wrap set needed before you can judge the sunscreen claim?
The UV400 lens was the only sunlit condition that kept the beads fully white. What does the tinted-lens result say about the claim "any dark lens protects your eyes"?
What can the beads not tell you about sunscreen or lenses? Think about which ultraviolet wavelengths the beads respond to.
Modification for Distance Learning
Students analyze the sample data above, or test beads at home in a window and outdoors if beads are mailed with the course kit, and post a short claim, evidence and reasoning paragraph for each product claim.
3
Fact-Check Desk
30 minPairs
Pairs act as fact-checkers for a school news site. Each pair picks one viral claim, finds at least three published sources about it (at least one must be a video or a trade book or magazine), rates each source, and writes a short fact-check that gives a verdict on validity and on reliability.
Claims to Choose From
"Himalayan salt lamps absorb the radiation given off by your electronics."
"Airline pilots and flight crews receive more cosmic radiation than people who work on the ground."
"Sunscreen does more harm to your skin than the ultraviolet light it blocks."
Procedure
Place the radiation named in the claim on Diagram 1 and write what its absorption does to tissue.
For each source, record the author, their expertise, the date, the evidence cited, and whether the author gains from the claim.
Write a 200-250 word fact-check with a headline verdict, the physics that decides validity, and the best and weakest source you found.
Scoring Checklist
The physics of photon energy or heating is stated correctly.
Validity and reliability are judged separately, each with a reason.
At least one source is identified as possibly biased, with the reason.
The verdict does not claim more certainty than the sources support.
Challenge Variation
Pairs trace their claim back to its earliest source they can find and describe how the wording changed each time it was repeated.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: The Electromagnetic Spectrum and What Absorption Does
The spectrum drawn on a logarithmic frequency axis, with band positions computed from their frequencies. The energy of each photon is proportional to frequency, so it rises from left to right. Photons above about 10 electron volts, in the highest-energy ultraviolet and beyond, can ionize atoms; lower-frequency radiation mainly heats matter or changes single molecules.
Diagram 2: Two Questions for Every Published Claim
A checklist for evaluating a claim about radiation. The left column tests validity against the physics of absorption; the right column tests the reliability of the source. Students answer both columns before writing a verdict.
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Homework Assignment
~30 min
HS-PS4-4 Homework: Evaluating Published Claims About Radiation
Directions: Every excerpt and source below is invented for practice. For each problem, answer in complete sentences. Keep validity (is it sound physics?) and reliability (can the source be trusted?) separate, and give a reason for each judgment. No calculations are needed.
Part 1: Frequency, Energy and Effects (Problems 1-2)
A hardware store sign says: "Our UV-blocking window film stops the sun's heat from entering your home." (a) Which parts of sunlight carry the energy that warms a room? (b) Is the claim valid? Explain what a UV-blocking film does and does not block. (c) What evidence should the store show to support a claim about heat?
An online article says airport millimeter-wave body scanners "fire ionizing radiation through your organs." These scanners use radio waves with frequencies of about 24-30 GHz. (a) Place this radiation on the spectrum and compare the energy of its photons with those of visible light and X-rays. (b) Is the claim valid? (c) Describe the only kind of effect absorbed millimeter waves could have on the body.
Part 2: Judging Sources (Problems 3-4)
Four sources discuss the claim "When the UV index is 8 or higher, unprotected skin can burn quickly": (A) a national weather service page that explains how the index is measured; (B) an anonymous forum post; (C) an advertisement from a sunscreen brand; (D) a nursing textbook with a list of references. Rank the sources from most to least reliable and explain each placement, naming any possible bias.
A seller claims its clear plastic food containers "block 100% of UV rays." Plan an investigation with UV-sensitive beads to test the claim. Name the independent variable, the controls you need, how many trials you would run, what result would support or refute the claim, and one limit on what the beads can tell you.
Part 3: Writing an Evaluation (Problems 5-6)
A magazine column says: "Cell phones have no effect of any kind on the body." Phones send and receive radio waves, and the Federal Communications Commission sets a limit on the rate at which tissue may absorb energy from a phone (1.6 watts per kilogram). (a) Is the column's claim valid as written? (b) Why does a limit on the rate of energy absorption make sense for radio waves? (c) Rewrite the claim so that it is valid.
Passage 1, from a trade book on atmospheric science by a climate scientist: "Ozone high in the atmosphere absorbs nearly all UV-C and much of the UV-B from the sun before it reaches the ground." Passage 2, from a personal blog: "Ozone loss doesn't matter, because ultraviolet is just light, like the light from a lamp." Write a claim, evidence and reasoning paragraph that evaluates the validity and reliability of both passages.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Physics of Absorption
Places the radiation on the spectrum and correctly describes its photon energy and its effect when absorbed (heating, molecular change or ionization)
Correct placement but the effect is missing or confused
Validity Judgment
Verdict on validity follows from the physics, including intensity or exposure where relevant, and notes overstatements
Verdict given with a general or partly incorrect reason
Reliability Judgment
Names specific features of the source (expertise, cited evidence, independent confirmation, bias) and uses them in the verdict
Mentions the source but does not say why it is or is not trustworthy
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Every excerpt and source in these questions is invented. Answer in words: no calculations are needed. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
A Wi-Fi router (radio waves), a TV remote (infrared), a desk lamp (visible light) and a CT scanner (X-rays) all give off electromagnetic radiation. Which list orders them from the lowest to the highest energy per photon?
Answer: C
Photon energy rises with frequency, and frequency rises from radio waves through infrared and visible light to X-rays. Choice A lists them from highest to lowest. Choice B swaps infrared and visible light: infrared lies just below red light in frequency. Choice D places the infrared remote below the radio waves of the router, but radio has the lowest frequency of the four.
Question 2 of 20 · Multiple Choice
A dim ultraviolet lamp and a very bright red lamp each shine on the same patch of skin for one minute. Which is more likely to damage DNA in the skin cells?
Answer: A
Whether one photon can alter a DNA molecule depends on the energy of that photon, which rises with frequency, and ultraviolet has a much higher frequency than red light. Choice B confuses intensity with photon energy: more red photons mean more warming, but no single red photon can do what one ultraviolet photon does. Choice C ignores that different frequencies carry different energies. Choice D is false: ultraviolet can alter DNA without ionizing atoms.
Question 3 of 20 · Multiple Choice
Which of these devices gives off ionizing radiation, whose photons can knock electrons out of atoms in living tissue?
Answer: D
Gamma-ray photons carry far more than the roughly 10 electron volts needed to ionize atoms, which is why they can kill microbes on medical supplies. The microwave oven (choice A) and the infrared remote (choice B) give off radiation that can only heat matter. The lamp (choice C) gives off visible light, whose photons can change single molecules, as in vision, but are too low in energy to ionize.
Question 4 of 20 · Multiple Choice
A neighborhood flyer says: "The FM radio tower on the hill bathes our homes in ionizing radiation that damages our DNA." Which evaluation is best?
Answer: B
FM radio photons carry more than a million times too little energy to ionize atoms, so the DNA claim is invalid no matter how powerful the tower is. Choice A is false: only the highest-frequency radiation ionizes. Choice C confuses total power with energy per photon. Choice D confuses reliability with validity: the physics can be checked even when the author is unknown.
Question 5 of 20 · Multiple Choice
Which source is the most reliable for the claim "Ultraviolet exposure raises the risk of skin cancer"?
Answer: C
The agency has medical expertise, cites evidence others can check, is dated and does not sell a product. Choice B confuses popularity with accuracy: likes do not measure evidence. Choices A and D both come from businesses that gain money from what readers believe about ultraviolet.
Question 6 of 20 · Multiple Choice
A company website says its phone sticker "neutralizes 95% of the radiation from phones and laptops," based on tests in the company's own lab. Which is a concern about reliability rather than validity?
Answer: B
Who ran the tests and whether anyone independent repeated them are questions about the source, which is reliability. Choices A, C and D are about the physics of the claim, which is validity. They are good criticisms, but they answer the other question.
Question 7 of 20 · Multiple Choice
A restaurant keeps fries warm under infrared heat lamps. A worker reads online that the lamps "irradiate the food and damage its DNA like X-rays." Which statement is valid?
Answer: A
Absorbed infrared makes molecules move faster, which is why the fries stay warm, but each photon carries far less energy than an X-ray photon. Choice C confuses the temperature of the lamp with the energy of each photon. Choice D contradicts the warming: energy that passed straight through could not heat the food. Choice B invents a difference between food and people that physics does not support.
Question 8 of 20 · Multiple Choice
A post warns that strawberries treated with gamma rays to kill bacteria "become radioactive and unsafe to eat." Which evaluation is best?
Answer: D
Gamma rays ionize atoms and break DNA, which kills bacteria, but becoming radioactive would require changing atomic nuclei, and the gamma rays used for food have too little energy to do that. Choice A is the error behind the post: exposure to radiation is not the same as becoming radioactive. Choice C is false, since the bacteria are killed only because the rays are absorbed.
Question 9 of 20 · Multiple Choice
Welders wear a mask with a dark special filter even when a weld lasts only a few seconds. Which explanation is best?
Answer: B
A welding arc emits strong ultraviolet, and each UV photon can damage molecules in the cells of the cornea, so a few seconds at close range can injure the eye. Choice C names radiation whose photons can only heat tissue. Choice D is false: hot metal glows with infrared and visible light, not gamma rays. Choice A is not about radiation.
Question 10 of 20 · Multiple Choice
A hospital pamphlet says radiation therapy aims high-energy X-rays at a tumor "because the X-rays ionize atoms and break the DNA in cancer cells." Evaluate the validity of this claim.
Answer: C
X-ray photons in therapy beams carry enormously more energy than needed to ionize atoms, so absorbed X-rays break DNA, which is how the treatment damages tumor cells. Choice A describes radio waves or microwaves. Choice B is only partly true, since some X-rays pass through, but those that are absorbed do the work. Choice D confuses reliability (a trustworthy source) with validity (sound physics).
Question 11 of 20 · Multiple Choice
A ski shop blog says: "Snow reflects much of the sun's ultraviolet, so you can sunburn faster on the slopes." What would most improve the reliability of this post?
Answer: D
Measurements by an independent agency are evidence that a reader can check. Choices A and B are anecdotes: they show that sunburns happen, not that snow is the reason. Choice C changes how the claim looks, not the evidence behind it.
Question 12 of 20 · Multiple Choice
In an online video, a homeowner says her headaches stopped the week after the utility removed her smart meter. What is the main weakness of this evidence?
Answer: A
A single anecdote cannot separate the meter from other causes such as stress, sleep or weather, and there is no comparison group. Choice B is false physics: smart meters use radio waves. Choice C overstates the case: a video can be reliable if it presents checkable evidence from experts.
Question 13 of 20 · Multiple Choice
Workers in a hospital X-ray department wear badges that record their total radiation exposure each month. Why track the total?
Answer: D
Each ionizing photon has some chance of damaging DNA, so small exposures add up over months. Choice A repeats the error that exposure makes a person radioactive. Choice B ignores that total dose, not a single moment, sets the risk. Choice C treats X-rays like infrared, whose main effect is heating.
Question 14 of 20 · Multiple Choice
Two articles make the same claim: "Years of unprotected ultraviolet exposure can damage the eyes." Article 1 is on the website of a national eye-care professional association and cites measurements. Article 2 is on a sunglasses store's website and cites nothing. Which statement is correct?
Answer: A
Validity depends on the claim and the physics: ultraviolet photons carry enough energy to damage cells, so the claim is sound wherever it appears. Reliability depends on the source, and Article 1 has expertise and cited evidence. Choice B confuses a biased source with a wrong claim: a seller can repeat a valid claim. Choice C makes the opposite mistake of letting the source decide the science.
Question 15 of 20 · Short Answer
Explain why you can get a sunburn on a cool, cloudy day at the beach but not from sitting close to a warm fireplace.
Sunburn comes from ultraviolet photons, which carry enough energy to damage molecules in skin cells, and much of the sun's ultraviolet passes through clouds. A fireplace gives off mostly infrared and visible light, whose photons only warm the skin. How warm you feel does not tell you how much energy each photon carries.
Question 16 of 20 · Short Answer
A magazine article says: "Radio waves and gamma rays are both electromagnetic radiation, so they are equally dangerous." Evaluate the validity of this claim.
Invalid. Both are electromagnetic radiation, but a gamma-ray photon carries more than ten billion times the energy of a radio photon. Gamma rays can ionize atoms and break DNA; absorbed radio waves only warm tissue, and only noticeably at high intensity. Belonging to the same family does not make two kinds of radiation equally harmful.
Question 17 of 20 · Short Answer
An invented blog post from a company that sells "EMF-blocking" bed canopies says: "Top scientists agree that the radiation from your router causes cancer while you sleep. Order today, before they ban the truth!" Identify two signs of possible bias or low reliability.
Any two of: the author sells the product the claim promotes; no scientists or studies are named, so "top scientists agree" cannot be checked; the post uses urgency and fear ("order today") in place of evidence; it suggests a hidden conspiracy ("before they ban the truth") instead of citing data.
Question 18 of 20 · Short Answer
A student tests a "UV-protective" umbrella. Beads under the umbrella stay pale, and beads in open sun turn dark purple. She concludes: "The umbrella blocks all UV." Evaluate her conclusion.
The result supports the claim that the umbrella blocks much of the direct UV, but it does not show that it blocks "all" UV. Pale beads may still have absorbed a little ultraviolet, the beads respond only to some UV wavelengths, UV reflected from sand, water or pavement can reach a person under an umbrella, and one trial is not enough. A valid conclusion would be "the umbrella greatly reduced the UV reaching the beads in this test."
Question 19 of 20 · Short Answer
A travel blog says: "Reaching into the airport baggage X-ray tunnel for a second is harmless. It's just a quick flash, like a camera flash." Evaluate the validity of the comparison.
Invalid comparison. A camera flash is visible light, whose photons cannot ionize atoms, so a brief flash is harmless. The tunnel uses X-rays, and each X-ray photon carries enough energy to ionize atoms and break DNA by itself, so even a brief exposure is not the same as a flash of light. The risk from one second may be small, but the curtains and shielding exist because the radiation is ionizing, and "harmless" is stronger than the physics allows.
Question 20 of 20 · Short Answer
A newspaper columnist writes: "When I was a child, shoe stores used X-ray machines to check how shoes fit. I was X-rayed dozens of times and I'm fine, so X-rays are harmless." Evaluate the validity and reliability of this claim.
Validity: invalid. X-ray photons are ionizing, and whether they cause lasting harm is a matter of chance, so one person staying healthy does not show that X-rays are safe. Reliability: low. The evidence is a single personal story with no measurements and no comparison group, and people who were harmed are not in the column.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-PS4-4 mean?
HS-PS4-4 asks students to evaluate published claims about what electromagnetic radiation does when matter absorbs it, judging both whether the claim is sound science and whether the source can be trusted. The science focus is that higher-frequency radiation carries more energy per photon, and that damage to living tissue depends on that energy. The code means High School, Physical Science, core idea 4 (Waves and Their Applications in Technologies for Information Transfer), performance expectation 4.
Is HS-PS4-4 taught in physics, chemistry or biology?
HS-PS4-4 is usually taught in Physics or Physical Science, often in a unit on waves and light. It connects naturally to biology (DNA damage and cancer) and to health classes, and some schools teach it as part of an integrated science course.
What is the assessment boundary for HS-PS4-4?
The official Assessment Boundary says: "Assessment is limited to qualitative descriptions." Students describe and compare the effects of different frequencies in words; they are not asked to calculate photon energies. Teachers can mention that photon energy is proportional to frequency without turning it into a calculation.
What is the difference between validity and reliability of a claim?
Validity is about whether the claim itself agrees with the science and the evidence; reliability is about whether the source can be trusted. A claim can be valid but posted by an unreliable source, or come from a respected source and still be overstated, so students should judge the two separately.
Why is ultraviolet light more harmful than visible light?
Ultraviolet photons have a higher frequency, so each one carries more energy than a photon of visible light. That extra energy is enough to rearrange bonds in DNA, which is why ultraviolet causes sunburn and raises skin cancer risk, while visible light of ordinary brightness does not.
Which types of electromagnetic radiation are ionizing?
Gamma rays, X-rays and the highest-energy part of the ultraviolet range are ionizing. Their photons carry more than about 10 electron volts, enough to knock electrons out of atoms. Radio waves, microwaves, infrared, visible light and most ultraviolet are non-ionizing, although ultraviolet can still damage DNA.
Do microwave ovens make food radioactive?
No. Microwaves heat food by making water molecules rotate and bump into their neighbors. Their photons carry far too little energy to ionize atoms, so the energy the food absorbs simply makes it hot.
How can students tell whether a website or video about radiation is biased?
Students should ask whether the author gains from the claim, through sales, clicks or sponsors, and whether the evidence can be checked. Warning signs include a product link next to a health claim, no named experts or studies, emotional or urgent language, and words like "always", "never" or "100%". A sponsored source is not automatically wrong, but its claims need independent confirmation.
Do students need to calculate photon energy for HS-PS4-4?
No. HS-PS4-4 is assessed with qualitative descriptions only. Students should know that energy per photon rises with frequency and be able to rank the bands of the spectrum, but calculations with E = hf belong to other lessons.
What comes after HS-PS4-4?
HS-PS4-5 is the natural next step: students communicate how devices such as solar cells, medical imaging systems and communication networks use wave behavior and absorption to transmit and capture information and energy. HS-PS4-4 also builds the source-evaluation skills used in science literacy standards such as RST.11-12.8.
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Related Standards
5 standards
These standards connect to HS-PS4-4: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-PS4-2Prerequisite
Model how waves are reflected, absorbed or transmitted through various materials
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