Topic 3: Waves

Question 1

What happens when white light is shone into a triangular prism?

Answer 1

disperses into colours - different wavelengths are refracted by different amounts

Question 2

What does refractive index tell you?

Answer 2

how fast light travels in that material

Question 3

refractive index, speed of light in vacuum and speed of light in material equation

Answer 3

refractive index = speed of light in vacuum/ speed of light in material

Question 4

What is the speed of light in a vacuum? (refractive index)

Answer 4

1.00

Question 5

What is Snell’s law?

Answer 5

n = sin(i)/ sin(r)

Question 6

What is the critical angle?

Answer 6

when the angle of refraction = 90

Question 7

What happens when the angle of incidence is above the critical angle?

Answer 7

total internal reflection

Question 8

The higher the refractive index…

Answer 8

the lower the critical angle

Question 9

How do you work out the critical angle?

Answer 9

Sin C = 1/ n (refractive index)

Question 10

2 uses of total internal reflection

Answer 10

-optical fibres
-prisms (periscope)

Question 11

Total internal reflection: prisms (periscope)

Answer 11

-ray of light shines into one prism and is totally internally reflected by 90
-light travels through another prism and is totally internally reflected by 90
-ray is now travelling parallel to its original path

Question 12

Sounds waves are…

Answer 12

longitudinal

Question 13

Sound travels fastest in…

Answer 13

denser mediums

Question 14

What can be used to measure sound waves?

Answer 14

oscilloscope

Question 15

The greater the amplitude of the wave…

Answer 15

the more energy it carries

Question 16

The higher the frequency of a sound wave…

Answer 16

the higher the pitch

Question 17

Transverse waves

Answer 17

vibrations perpendicular to direction of travel

Question 18

Longitudinal waves

Answer 18

vibrations parallel to direction of travel

Question 19

Transverse waves examples

Answer 19

-EM
-light

Question 20

Longitudinal waves examples

Answer 20

-sound
-shock waves (seismic)

Question 21

Speed, frequency and wavelength equation

Answer 21

speed = frequency x wavelength

Question 22

What is the doppler effect?

Answer 22

the change in frequency or wavelength of a wave for an observer moving relative to its source

Question 23

Doppler effect examples

Answer 23

-if a car is moving away from you, the frequency of the wave will be lower
-if a car is moving towards you, the frequency of the wave will be higher

Question 24

(visible light) Red has the…

Answer 24

longest wavelength and lowest frequency

Question 25

(visible light) Violet has the…

Answer 25

shortest wavelength and highest frequency

Question 26

What are optical fibres used for?

Answer 26

-telephone and broadband internet cables
-medical equipment

Question 27

How do optical fibres work?

Answer 27

-made of plastic or glass, surrounded by cladding with a lower refractive index
-narrow core (light signals always hit the cladding at angles higher than C)
-light is always internally reflected