The Electromagnetic Spectrum Answer Key - Fill and Sign Printable ... - Free Printable

You’ve uploaded a worksheet titled “The electromagnetic spectrum” with 15 true/false questions. I’ll solve each question, provide the correct answer, and explain why.

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Question 1: Gamma rays travel faster than visible light.

✔ Answer: False

Explanation:
All electromagnetic waves — including gamma rays, visible light, radio waves, etc. — travel at the same speed in a vacuum: the speed of light (c = 3 × 10⁸ m/s). The speed does not depend on frequency or wavelength.

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Question 2: All electromagnetic waves travel at the same speed in a vacuum.

✔ Answer: True

Explanation:
Yes, this is a fundamental principle of electromagnetism. In a vacuum, all EM waves travel at c = 3.00 × 10⁸ m/s, regardless of their type.

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Question 3: The speed of light in a vacuum is ___ 300,000,000 m/s?

✔ Answer: True

Explanation:
300,000,000 m/s = 3 × 10⁸ m/s, which is the accepted value for the speed of light in a vacuum (rounded to 3 significant figures).

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Question 4: White light is a mixture of colours that can be split into the visible spectrum by a rainbow, prism, or diffraction grating.

✔ Answer: True

Explanation:
White light is composed of all visible wavelengths (colors). A prism or diffraction grating disperses it into its component colors via refraction or diffraction — this is how rainbows form too.

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Question 5: Which of the following has the highest frequency?

Options: ultraviolet, microwaves, x-rays, radiowaves

✔ Answer: X-rays

Explanation:
Order of EM waves from lowest to highest frequency:
Radio → Microwaves → Infrared → Visible → Ultraviolet → X-rays → Gamma rays
So X-rays have higher frequency than UV, microwaves, and radio waves.

*(Note: Gamma rays have even higher frequency than X-rays, but they’re not listed here.)*

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Question 6: Which of the following has the longest wavelength?

Options: visible light, microwaves, infrared, radiowaves

✔ Answer: Radiowaves

Explanation:
Wavelength is inversely proportional to frequency. Radiowaves have the lowest frequency, so they have the longest wavelength among the options.

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Question 7: Which of the following has the longest wavelength?

Options: gamma rays, x-rays, microwaves, ultraviolet

✔ Answer: Microwaves

Explanation:
Among these, microwaves have the lowest frequency → longest wavelength.
Order (longest to shortest wavelength): Microwaves > Ultraviolet > X-rays > Gamma rays.

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Question 8: Which of the following has the shortest wavelength?

Options: visible light, infrared, ultraviolet, radiowaves

✔ Answer: Ultraviolet

Explanation:
Shortest wavelength = highest frequency. Among these:
Ultraviolet > Visible > Infrared > Radiowaves
So ultraviolet has the shortest wavelength.

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Question 9: Which of the following has the lowest frequency?

Options: ultraviolet, microwaves, x-rays, radiowaves

✔ Answer: Radiowaves

Explanation:
Radiowaves have the lowest frequency in the EM spectrum (among common categories), so they are correct here.

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Question 10: These waves have the longest wavelength and are used in some signals for radar, TV, and radio.

Options: gamma rays, x-rays, microwaves, ultraviolet

✔ Answer: Microwaves

Explanation:
Microwaves are used in radar, satellite communications, TV, and mobile phones. They have longer wavelengths than visible/UV/X-rays, though radiowaves have even longer — but radiowaves aren’t an option here.
*Note: Some radar uses microwaves, others use radio waves — but since “microwaves” is the best available choice, it’s correct.*

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Question 11: These rays are absorbed by bones and teeth but pass through flesh.

Options: gamma rays, x-rays, microwaves, ultraviolet

✔ Answer: X-rays

Explanation:
X-rays penetrate soft tissue but are absorbed by denser materials like bones and teeth — that’s why they’re used in medical imaging.

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Question 12: These waves are used to cook food (they are absorbed by water molecules in the food).

Options: gamma rays, x-rays, microwaves, ultraviolet

✔ Answer: Microwaves

Explanation:
Microwave ovens work because microwaves (around 2.45 GHz) are strongly absorbed by water molecules, causing them to vibrate and heat up the food.

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Question 13: Our eyes are able to see this part of the electromagnetic spectrum.

Options: ultraviolet, radio, visible, infrared

✔ Answer: Visible

Explanation:
Human eyes detect wavelengths between approximately 400 nm (violet) and 700 nm (red) — this is the visible spectrum.

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Question 14: Any warm object emits this radiation. Higher temperature objects emit this type of wave.

Options: gamma rays, x-rays, visible light, infrared

✔ Answer: Infrared

Explanation:
All objects above absolute zero emit infrared radiation. Hotter objects emit more IR and may also emit visible light (like red-hot iron). This is called blackbody radiation.

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Question 15: These rays are emitted by the sun and cause sunburn. High doses can lead to skin cancer.

Options: gamma rays, ultraviolet, microwaves, infrared

✔ Answer: Ultraviolet

Explanation:
UV radiation from the sun damages skin cells, causes sunburn, and over time can lead to skin cancer. That’s why sunscreen blocks UV rays.

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## ✔ Final Answer Key:

| Q# | Answer |
|----|-------------|
| 1 | False |
| 2 | True |
| 3 | True |
| 4 | True |
| 5 | X-rays |
| 6 | Radiowaves |
| 7 | Microwaves |
| 8 | Ultraviolet |
| 9 | Radiowaves |
| 10 | Microwaves |
| 11 | X-rays |
| 12 | Microwaves |
| 13 | Visible |
| 14 | Infrared |
| 15 | Ultraviolet |

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