Electromagnetic Spectrum

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Notes

Electromagnetic Waves

The **electromagnetic spectrum** is arranged in order of **wavelength** or **frequency**.
Regions with long wavelength have low frequency and vice versa.
Order from longest to shortest wavelength: **radio waves**, **microwaves**, **infrared**, **visible light**, **ultraviolet**, **X-rays**, **gamma rays**.
Visible light is a small part of the EM spectrum.
All EM waves are **transverse waves** that transfer energy.
All EM waves travel at the same high speed in a vacuum: **3.0 × 10⁸ m/s**.

Uses of Electromagnetic Waves

**Radio waves**: radio and television transmissions, radar.
**Microwaves**: satellite TV, mobile phones, microwave ovens.
**Infrared**: TV remote controllers, thermal imaging.
**Visible light**: vision, photography.
**Ultraviolet**: detecting fake banknotes.
**X-rays**: medical scanning, security scanners.
**Gamma rays**: detection and treatment of cancer.

Dangers of Electromagnetic Waves

As frequency increases, **energy** of EM waves increases.
Beyond visible (UV, X-rays, gamma rays) waves are **ionising** – they can remove electrons from atoms.
Higher frequency EM waves are more ionising.
**Ultraviolet**: damages surface cells and eyes, leading to skin cancer and eye conditions.
**X-rays and gamma rays**: can cause mutation or damage to cells in the body, leading to cancer.
Sunscreen absorbs UV; good sunglasses absorb UV to protect eyes.

The electromagnetic spectrum showing regions from radio to gamma rays, with decreasing wavelength and increasing frequency.

Practice questions

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1.Arrange the following regions of the electromagnetic spectrum in order of decreasing wavelength (longest first).
Easy
- ultraviolet
- microwaves
- visible light
- radio waves
2.Which of the following is the correct order of the electromagnetic spectrum from longest to shortest wavelength?
Easy
- ARadio waves, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays
- BGamma rays, X-rays, ultraviolet, visible, infrared, microwaves, radio waves
- CVisible, infrared, radio waves, microwaves, ultraviolet, X-rays, gamma rays
- DMicrowaves, radio waves, infrared, visible, ultraviolet, gamma rays, X-rays
3.All electromagnetic waves travel at the same speed in a vacuum.
Easy
True or false?
4.State one use of microwaves.
Easy
5.State two harmful effects of excessive exposure to ultraviolet radiation.
Medium
6.Complete the sentence:
Medium
The electromagnetic spectrum is arranged in order of decreasing $____ and$ increasing ____.
7.What is the speed of electromagnetic waves in a vacuum? Give your answer in m/s.
Medium
- A300000000
- B360000000
- C330000000
- D270000000
8.Which type of electromagnetic radiation is used for thermal imaging?
Medium
- AInfrared
- BUltraviolet
- CMicrowaves
- DRadio waves

Slides

The Electromagnetic Spectrum

The electromagnetic spectrum is a continuous range of waves arranged by wavelength or frequency.
Longer wavelength means lower frequency, and vice versa.
The main regions in order of decreasing wavelength: Radio, Microwaves, Infrared, Visible, Ultraviolet, X-rays, Gamma rays.

Which of the following is the correct order of the electromagnetic spectrum from longest to shortest wavelength?

Gamma rays, X-rays, Ultraviolet, Visible, Infrared, Microwaves, Radio
Radio, Microwaves, Infrared, Visible, Ultraviolet, X-rays, Gamma rays
Radio, Infrared, Microwaves, Visible, Ultraviolet, Gamma rays, X-rays
Visible, Infrared, Radio, Microwaves, Ultraviolet, X-rays, Gamma rays

Properties of EM Waves

All electromagnetic waves are transverse waves that transfer energy from source to absorber.
They all travel at the same speed in a vacuum: $3.0 \times$ 10⁸ m/s.
This speed is approximately the same in air.

Electromagnetic waves $are ____$ waves that transfer ____ from the source to an absorber.

Uses of EM Waves

Radio waves: radio and television transmissions, radar.
Microwaves: satellite TV, mobile phones, microwave ovens.
Infrared: TV remote controls, thermal imaging.
Visible light: vision, photography.
Ultraviolet: detecting fake banknotes.
X-rays: medical scanning, security scanners.
Gamma rays: detection and treatment of cancer.

Which of these are correct uses of electromagnetic waves?

Microwaves are used in satellite television.
Infrared is used for detecting fake banknotes.
X-rays are used for medical scanning.
Gamma rays are used in TV remote controls.

Dangers of EM Waves

As frequency increases, energy increases. Beyond visible light, waves can ionise atoms.
Ultraviolet: damages surface cells and eyes, can cause skin cancer and eye conditions.
X-rays and gamma rays: can penetrate the body, cause mutation or damage to cells, leading to cancer.

Which type of electromagnetic wave is most ionising?

Radio waves
Infrared
Ultraviolet
Gamma rays

Harmful Effects of Ultraviolet

UV is invisible but carries high energy, similar to visible light.
Exposure can cause severe eye damage; good sunglasses absorb UV.
UV can kill cells or cause them to malfunction, leading to premature ageing and skin cancer.
Sunscreen absorbs UV light to protect the skin.

Sunscreen absorbs ____ light, preventing it from damaging the skin.

Harmful Effects of X-rays and Gamma Rays

X-rays and gamma rays are the most ionising EM waves.
They can penetrate the body and cause internal damage.
They can cause mutation of DNA, leading to cancer.

Which of these are harmful effects of excessive exposure to X-rays or gamma rays?

They can cause DNA mutation.
They can cause skin cancer.
They can penetrate the body and cause internal damage.
They are used in TV remote controls.

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