Waves

Question 1

What is the frequency of a wave?

Answer 1

The number of waves that pass a point per second

Question 2

What is the amplitude of a wave?

Answer 2

The height of a wave from rest to crest

Question 3

What is the period of a wave?

Answer 3

The time it takes for one complete wave to pass a point

Question 4

What is the wavefront of a wave?

Answer 4

An imaginary surface that represents corresponding points on waves vibrating in unison.

Question 5

What is the Doppler effect

Answer 5

The Doppler effect is when there is a change in the observed frequency and wavelength of a wave when the source is moving relative to an observer.

Question 6

Explain the Doppler effect

Answer 6

For example:
1. When a source is moving away from an observer, the waves it emits bunch up in front of it and spread out behind it.
2. This causes the observer to observe an increase in wavelength and decrease in frequency of the waves emitted from the source.

Question 7

List the order of the electromagnetic spectrum in terms of increasing frequency and decreasing wavelength

Answer 7

1. radio waves
2. microwaves
3. infrared waves
4. visible light
5. ultraviolet light
6. X-rays
7. gamma rays

Question 8

Name the colours of the visible light spectrum in terms of increasing frequency

Answer 8

1. red
2. orange
3. yellow
4. green
5. blue
6. violet

Question 9

what are the uses of radio waves?

Answer 9

broadcasting and communications

Question 10

what are the uses of microwaves?

Answer 10

cooking and satellite transmissions

Question 11

what are the uses of infrared?

Answer 11

heaters and night vision equipment

Question 12

what are the uses of visible light?

Answer 12

optical fibres and photography

Question 13

what are the uses of ultraviolet?

Answer 13

fluorescent lamps

Question 14

what is the use of X-rays?

Answer 14

Observing the internal structure of objects and materials, including for medical procedures

Question 15

what are the uses of gamma rays?

Answer 15

sterilising food and medical equipment

Question 16

What is the danger of microwaves?

Answer 16

1. internal heating of body tissue
2. microwave ovens have shielding to prevent microwaves from reaching the user

Question 17

What is the danger of infrared?

Answer 17

1. skin burns
2. wear protective clothing such as oven gloves

Question 18

What are the dangers of ultraviolet?

Answer 18

1. damage to surface cells and blindness
2. wear sunscreen with UV filters and stay out of strong sunlight

Question 19

What are the dangers of gamma rays

Answer 19

1. cancer and mutation
2. radioactive sources of gamma rays should be kept in lead-lined boxes

Question 20

What is the critical angle?

Answer 20

The incident angle that gives total internal reflection when exceeded.

Question 21

How is total internal reflection used in optical fibres?

Answer 21

The core of the fibre is so narrow that light passing through it always hits the core-cladding boundary at angles greater than the critical angle, so is always totally internally reflected.

Question 22

How is total internal reflection used in prisms?

Answer 22

1. Prisms are used in a periscope to see things that aren’t in our line of sight.
2. The ray of light travels into one prism at an angle greater than C so it is totally internally reflected at 90 degrees.
3. It then travels into another prism below and is totally internally reflected at 90 degrees again.
4. The ray is now travelling parallel to its initial path but at a lower height.