Electromagnetic spectrum worksheet with questions on wave properties and applications.

Let's go through each question in the worksheet "The electromagnetic spectrum" and solve them step by step, explaining the reasoning behind each answer.

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1. Gamma rays travel faster than visible light.

- Answer: False
- Explanation: All electromagnetic waves, including gamma rays and visible light, travel at the same speed in a vacuum — the speed of light (about 300,000 km/s). So, gamma rays do not travel faster than visible light.

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

- Answer: True
- Explanation: This is a fundamental property of electromagnetic waves. In a vacuum, all EM waves (radio, microwaves, infrared, visible light, UV, X-rays, gamma rays) travel at the speed of light: 300,000,000 m/s.

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3. The speed of light in a vacuum is...

- Answer: 300,000,000 m/s
- Explanation: The speed of light in a vacuum is approximately 3 × 10⁸ m/s, which is 300,000,000 meters per second. This is a standard value used in physics.

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4. While light is a mixture of colours that can be split into the visible spectrum by a ...

- Answer: prism
- Explanation: A prism refracts (bends) different wavelengths of light by different amounts, dispersing white light into its component colors (the visible spectrum). This is called dispersion.

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5. Which of the following has the highest frequency?

- Options: ultraviolet, microwaves, x-rays, radiowaves
- Answer: x-rays
- Explanation: Frequency increases from radio waves → microwaves → infrared → visible light → ultraviolet → X-rays → gamma rays. X-rays have higher frequency than ultraviolet, microwaves, and radio waves.

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6. Which of the following has the highest frequency?

- Options: visible light, microwaves, infrared, radiowaves
- Answer: visible light
- Explanation: Among these, visible light has the highest frequency. Order from low to high frequency:
radiowaves < microwaves < infrared < visible light

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7. Which of the following has the longest wavelength?

- Options: gamma rays, visible light, ultraviolet, radiowaves
- Answer: radiowaves
- Explanation: Wavelength is inversely related to frequency. Radiowaves have the longest wavelengths in the EM spectrum (can be kilometers long), while gamma rays have the shortest.

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8. Which of the following has the shortest wavelength?

- Options: gamma rays, visible light, ultraviolet, radiowaves
- Answer: gamma rays
- Explanation: Gamma rays have the shortest wavelengths (less than 0.01 nanometers), making them the most energetic form of EM radiation.

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9. Which of the following has the lowest frequency?

- Options: ultraviolet, microwaves, x-rays, radiowaves
- Answer: radiowaves
- Explanation: Radiowaves have the lowest frequencies in the EM spectrum, often measured in kilohertz or megahertz.

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10. These waves are used to carry signals for radar, TV and radio

- Options: radiowaves, ultraviolet, microwaves, infrared
- Answer: radiowaves
- Explanation: Radiowaves are used for broadcasting (TV, radio) and radar systems. Microwaves are also used for some communications (e.g., satellite), but "radiowaves" is the best general answer here.

> Note: Some might argue microwaves are used for radar, but since both options are listed and "radiowaves" is broader and includes many communication uses, it's acceptable. However, microwaves are actually more accurate for radar and satellite links. But based on typical school-level teaching, radiowaves is likely expected.

But let’s clarify:
- Radar uses microwaves
- TV and radio use radiowaves

So if only one choice is allowed, radiowaves covers TV and radio, but not radar. However, microwaves are used in radar and some TV signals.

Given the options, microwaves may be better for radar, but the question says "radar, TV and radio".

Since radiowaves are used for TV and radio, and microwaves for radar, but microwaves are a subset of radio waves, and the term "radiowaves" is often used broadly.

But strictly speaking, microwaves are used for radar and satellite TV.

Wait — let’s look again:
- Radar: microwaves
- TV: both VHF/UHF (radiowaves) and satellite (microwaves)
- Radio: radiowaves

So the best single answer covering all three is microwaves?

Actually, no — radiowaves include lower frequencies used for AM/FM radio and TV. Microwave is a subcategory.

But in many curricula, microwaves are associated with radar and satellite, while radiowaves are for radio/TV.

But microwaves are technically part of the radio wave family.

However, since microwaves are used for radar, and radiowaves for TV/radio, and the question lists all three, the best answer is likely:

👉 radiowaves — because they cover TV and radio, and radar often uses microwave band, but microwaves are sometimes grouped under "radio waves".

But in multiple-choice questions like this, microwaves is often the correct choice for radar.

Wait — the options are:
- radiowaves
- ultraviolet
- microwaves
- infrared

So microwaves is the correct choice for radar, and radiowaves for TV and radio.

But since microwaves are used for radar and some TV signals, and radiowaves for others, but microwaves are specifically linked to radar.

But the question says: “used to carry signals for radar, TV and radio”

So we need a wave type that covers all three.

Only radiowaves (including microwaves) can reasonably cover all.

But microwaves are a subset.

So, radiowaves is the best choice.

✔ Answer: radiowaves

(Though in reality, microwaves are used for radar and satellite TV, and radiowaves for broadcast TV/radio. But in education, radiowaves is the broad category.)

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

- Options: radio, microwaves, x-rays, infrared
- Answer: x-rays
- Explanation: X-rays are absorbed by dense materials like bones and teeth but pass through soft tissues like flesh. That’s why they’re used in medical imaging.

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

- Options: ultraviolet, radio, microwaves, infrared
- Answer: microwaves
- Explanation: Microwaves cause water molecules to vibrate, generating heat. This is how microwave ovens work.

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13. Our eyes are able to see waves in this part of the electromagnetic spectrum

- Options: ultraviolet, radio, microwaves, visible
- Answer: visible
- Explanation: The human eye can detect only visible light (wavelengths ~400–700 nm). Other types are invisible.

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14. Any warm object emits this. Night vision cameras are able to detect this type of wave

- Options: gamma rays, visible light, microwaves, infrared
- Answer: infrared
- Explanation: All warm objects emit infrared radiation. Night vision devices detect infrared to see in the dark.

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15. These are rays emitted by the sun (and other hot objects). Over-exposure to these rays can harm the skin and cause cancer.

- Options: gamma rays, ultraviolet, microwaves, infrared
- Answer: ultraviolet
- Explanation: The sun emits UV rays, which can damage skin cells and lead to skin cancer. UV rays are also produced by very hot objects.

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✔ Final Answers:

| Question | Answer |
|--------|--------|
| 1 | False |
| 2 | True |
| 3 | 300,000,000 m/s |
| 4 | prism |
| 5 | x-rays |
| 6 | visible light |
| 7 | radiowaves |
| 8 | gamma rays |
| 9 | radiowaves |
| 10 | radiowaves |
| 11 | x-rays |
| 12 | microwaves |
| 13 | visible |
| 14 | infrared |
| 15 | ultraviolet |

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🔍 Summary Tips:

- Frequency ↑ → Energy ↑ → Wavelength ↓
- Gamma rays = highest energy, shortest wavelength
- Radio waves = lowest energy, longest wavelength
- Visible light = middle of the spectrum, what we can see
- UV & X-rays = harmful, ionizing radiation
- Infrared = heat radiation
- Microwaves = cooking, radar, comms
- Radio waves = broadcasting

Use the electromagnetic spectrum order as a guide:
> Radio → Microwaves → Infrared → Visible → Ultraviolet → X-rays → Gamma rays

Remember: ROYGBIV for visible light (Red, Orange, Yellow, Green, Blue, Indigo, Violet)

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Let me know if you'd like a printable version or a diagram!