6.2 Waves (electromagnetic waves)

Question 1

What type of spectrum do electromagnetic waves form?

Answer 1

a continuous spectrum

Question 2

Order the types of electromagnetic radiation from lowest to highest frequency

Answer 2

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

Question 3

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

Answer 3

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

Question 4

What property of waves in different mediums causes refraction?

Answer 4

• velocity
• wave speed is slower in denser materials, causing refraction

Question 5

In which direction (relative to the normal) do waves refract when entering a denser medium?

Answer 5

• they bend towards the normal
• the angle of refraction is less than the angle of incidence

Question 6

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

Answer 6

radio waves

Question 7

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

Answer 7

When radio waves are absorbed, they can induce oscillations in a circuit with the same frequency as the waves themselves

Question 8

Where do gamma rays originate from?

Answer 8

They originate from changes in the nuclei of atoms

Question 9

What health effects can ultraviolet waves cause?

Answer 9

• they can cause the skin to age prematurely
• they can increase the risk of developing skin cancer

Question 10

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

Answer 10

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

Question 11

Give three practical uses for infrared radiation

Answer 11

1. electrical heaters
2. cooking
3. infrared cameras

Question 12

Give two practical uses for microwave radiation

Answer 12

1. satellite communications
2. cooking food

Question 13

Give two practical uses for radio waves

Answer 13

1. television transmission
2. radio transmission

Question 14

What wave phenomenon is used by lenses to form an image?

Answer 14

refraction

Question 15

How does a convex lens form an image?

Answer 15

Parallel rays of light are refracted and brought together at a point known as the principal focus

Question 16

What is meant by the focal length of a lens?

Answer 16

the distance from the lens to the principal focus

Question 17

What is the difference between the image produced by a convex lens and a concave lens?

Answer 17

• convex lenses can produce real or virtual images
• concave lenses can only produce virtual images

Question 18

Why does magnification not have a unit?

Answer 18

• it is the ratio between image height and object height
• and ratios do not require units

Question 19

What symbol is used to represent a convex lens in a ray diagram?

Question 20

What symbol is used to represent a concave lens in a ray diagram?

Question 21

What determines the colour of visible light waves?

Answer 21

the wavelength and the frequency of the light waves

Question 22

What colour of visible light has the highest frequency?

Answer 22

blue

Question 23

What colour of visible light has the largest wavelength?

Answer 23

red

Question 24

What is meant by the term ‘specular reflection’?

Answer 24

reflection from a smooth surface in a single direction

Question 25

What is meant by the term ‘diffuse reflection’?

Answer 25

reflection from a rough surface which causes scattering

Question 26

How does a red colour filter work?

Answer 26

• a red filter absorbs all wavelengths of light other than those in the red range of the spectrum
• this means that only red light passes through the filter

Question 27

What determines the colour of an opaque object?

Answer 27

• different objects reflect different wavelengths of light by different amounts
• the wavelengths that are most strongly reflected determine the colour

Question 28

What happens to the wavelengths of light that aren’t reflected by an opaque object?

Answer 28

any wavelengths that aren’t reflected are absorbed by the object

Question 29

What colour does an object appear if all wavelengths are reflected by equal amounts?

Answer 29

white

Question 30

What colour does an object appear if all wavelengths are absorbed?

Answer 30

black