5. Light and The Electromagnetic Spectrum

Question 1

What types of waves are electromagnetic (EM) waves?

Answer 1

Transverse

Question 2

What do electromagnetic waves transfer?

Answer 2

Energy (not matter).

Question 3

What type of spectrum do electromagnetic waves form?

Answer 3

A continuous spectrum (EM spectrum)

Question 4

List the order of the EM spectrum in order of increasing frequency and decreasing wavelength

Answer 4

1. Radio waves
2. Microwaves
3. Infrared
4. Visible light
5. Ultraviolet (UV)
6. X-rays
7. Gamma rays

Question 5

What is the highest frequency electromagnetic wave?

Answer 5

Gamma waves

Question 6

What is the highest energy electromagnetic wave?

Answer 6

Gamma waves

Question 7

What properties are shared by all electromagnetic waves?

Answer 7

• They are all transverse waves.
• They all travel at the same speed (3 x 10⁸ m/s)
• They can travel through a vacuum.
• Do not need particles to move.

Question 8

What range of frequencies of EM waves can be detected by the human eye?

Answer 8

400-700 nanometres

Question 9

How do the speeds of EM radiation differ in a vacuum and in air?

Answer 9

Electromagnetic waves all travel at the same speed in a vacuum and in air.

Question 10

What can happen when radiation strikes an object?

Answer 10

It can be:
- transmitted
- reflected
- absorbed

Question 11

What type of waves can be produced by oscillations in an electrical circuit?

Answer 11

Radio waves

Question 12

How can radio waves create an alternating current in a circuit?

Answer 12

When radio waves are absorbed, it causes electrons in the receiver to oscillate so there is an alternating current of the same frequency as radio waves that are induced in the receiver.

Question 13

Where do gamma rays originate from?

Answer 13

Gamma rays are created by changes in an atom’s nucleus.

Question 14

What health effects can ultraviolet waves cause?

Answer 14

• They can cause the skin to age prematurely.
• They are ionising radiation so can increase the risk of developing skin cancer.

Question 15

What health effects can X-rays and gamma rays cause?

Answer 15

• They are ionising radiation so can cause mutations in genes.
• They can lead to increased risk of developing various cancers.

Question 16

What health effects can infrared rays cause?

Answer 16

Infrared waves can cause burns to skin/tissue.

Question 17

How does electromagnetic radiation affect electron arrangement in atoms?

Answer 17

Absorption or emission of electromagnetic radiation can cause electron arrangement to change. (It can remove electrons from the atom or move electrons further from the nucleus).

Question 18

How do atoms become ions?

Answer 18

By losing an outer electron.

Question 19

What are the effects of body cells absorbing radiation?

Answer 19

Large amounts can damage cells.
Smaller amounts cause mutation, causing cells to divide rapidly, which can lead to cancer.

Question 20

List uses of radio waves and explain

Answer 20

• Broadcasting
• Satellite transmissions
• Communications

This is because radio waves have long wavelengths and can travel long distances without losing quality.

Question 21

State and explain uses of microwaves

Answer 21

• Cooking, as microwaves are absorbed by heat and fat/water foods.
• Communications
• Satellite transmissions

Question 22

State and explain uses of infrared radiation

Answer 22

• Cooking food, as it transfers thermal energy.
• Electric heaters
• Thermal imaging
• Optical fibres
• Security systems
• TV remote controls
• Short range communications

Question 23

State and explain uses of visible light

Answer 23

• Illumination
• Vision
• Photography

Question 24

State and explain uses of UV radiation

Answer 24

• Sterilisation, as it kills bacteria.
• Fluorescent lamps, as it radiates low heat but high energy making it efficient.
• Sun tanning
• Detecting forged bank notes
• Security marking

Question 25

State and explain uses of X-rays

Answer 25

• Medical imaging and treatment, as x-rays are very high in energy and can easily penetrate body tissues.
• Airport security scanners
• Looking inside objects

Question 26

State and explain uses of gamma rays

Answer 26

• Medical treatments, such as radiotherapy in the treatment of cancer.
• Sterilising food and medical equipment.

Question 27

Which waves of the EM spectrum are regarded as most dangerous and why?

Answer 27

Gamma and X-rays because they have the highest energy and frequency.