P5 - Light and the EM Spectrum

Question 1

name the two types of wave.

Answer 1

longitudinal and transverse

Question 2

define longitudinal wave.

Answer 2

parallel oscillations - along the direction of the energy transfer

Question 3

define transverse wave.

Answer 3

perpendicular oscillations - to the direction of energy transfer

Question 4

what is the difference between transverse and longitudinal waves?

Answer 4

longitudinal waves have parallel oscillations, whereas transverse waves have perpendicular oscillations

Question 5

name the 3 important features of a wave

Answer 5

1) amplitude
2) frequency
3) wavelength

Question 6

what is the amplitude of a wave?

Answer 6

the distance from the middle of the wave to the top or bottom of the wave

Question 7

define frequency.

Answer 7

the number of waves that go past a particular point per second

Question 8

define wavelength.

Answer 8

the distance from one point on a wave to the same point on the next wave

Question 9

name 2 types of longitudinal wave

Answer 9

• sound
• seismic

Question 10

is sound transverse or longitudinal?

Answer 10

longitudinal

Question 11

name 3 types of transverse wave.

Answer 11

• light
• heat (INFRARED)
• radio

Question 12

what do all waves do?

Answer 12

transfer energy from one place to another

Question 13

what do longitudinal waves require?

Answer 13

a medium to travel through

Question 14

which colour has the longest wavelength but lowest frequency?

Answer 14

red

Question 15

which colour has the shortest wavelength but highest frequency?

Answer 15

violet

Question 16

what is white light?

Answer 16

a combination of the 7 different colours in the visible light spectrum

Question 17

define black.

Answer 17

an absence of light

Question 18

define opaque.

Answer 18

does not transmit any light

Question 19

define dispersion.

Answer 19

tiny water droplets in air splitting up the colours in white light

Question 20

why do we only see 3 different colours (primary colours)?

Answer 20

3 types of cone cells in your eyes (in the retina)

Question 21

what is the angle of incidence equal to?

Answer 21

angle of reflection

Question 22

what is the angle of reflection equal to?

Answer 22

angle of incidence

Question 23

true or false?
the angle of incidence is equal to the angle of refraction

Answer 23

FALSE
equal to the angle of REFLECTION not REFRACTION

Question 24

true or false?
waves are always reflected

Answer 24

false

Question 25

name the 3 things which can happen to waves

Answer 25

1) absorbed 2) transmitted (leads to refraction) 3) reflected

Question 26

what happens when a wave is absorbed?

Answer 26

energy from the wave is transferred to the material's energy store

Question 27

what happens when a wave is transmitted?

Answer 27

wave enters the material but carries on travelling, which results in refraction

Question 28

what happens when a wave is reflected?

Answer 28

the wave never enters the material

Question 29

what is the name of the angle between the angle of incidence and the normal?

Answer 29

angle of incidence

Question 30

what is the name of the angle between the normal and the reflected ray?

Answer 30

angle of reflection

Question 31

is the normal parallel or perpendicular to the boundary on a ray diagram?

Answer 31

perpendicular

Question 32

name the two types of reflection

Answer 32

1) specular reflection 2) diffuse/scattered reflection

Question 33

what does specular reflection produce?

Answer 33

a clear image

Question 34

give an example of where we can see specular reflection

Answer 34

on mirrors

Question 35

true or false? the boundary in diffuse reflection is bumpy

Answer 35

true specular reflection has a flat boundary

Question 36

what happens to a light ray as it crosses a boundary from a less dense medium to a more dense medium?

Answer 36

it refracts

Question 37

explain why a shadow forms when an object is placed in front of a light source

Answer 37

- light travels in straight ray lines - the object absorbs the light - this causes a shadow

Question 38

if the angle of incidence is 35 degrees what will be the angle of reflection when a plain mirror is used? Why?

Answer 38

35 degrees - angle of incidence=angle of reflection

Question 39

define refraction

Answer 39

when waves change direction as they pass from one medium to another (i.e air into glass)

Question 40

true or false? waves travel at different speeds in different mediums

Answer 40

true

Question 41

name the 3 different rays shown in a refraction ray diagram

Answer 41

1) incident ray 2) refracted ray 3) emergent ray

Question 42

what happens to the speed of a wave as it travels from a less dense medium into a more dense medium?

Answer 42

wave slows down

Question 43

what happens to the speed of a wave as it travels from a more dense medium into a less dense medium?

Answer 43

wave speeds up

Question 44

what is the equation for wavespeed?

Answer 44

wavespeed = frequency x wavelength

Question 45

true or false? as the speed of a wave increases, the wavelength decreases

Answer 45

false the wavelength will increase also

Question 46

true or false? if the wave enters/ leaves the medium along the normal, the waves will not change direction

Answer 46

true

Question 47

what is the name of a line drawn at 90 degrees to the surface of a material?

Answer 47

the normal

Question 48

which term is used to refer to an incoming ray?

Answer 48

incident ray

Question 49

what is the law of reflection?

Answer 49

angle of incidence = angle of reflection

Question 50

which term is used to refer to regular reflection from a smooth surface in a single direction?

Answer 50

specular reflection

Question 51

which term is used to refer to the scattering of light by a rough surface?

Answer 51

diffuse reflection

Question 52

which is densest - air, water or glass?

Answer 52

glass

Question 53

what happens to a light ray when it travels from water into air?

Answer 53

it bends away from the normal

Question 54

which word is used to describe a light ray being passed through a material?

Answer 54

transmitted

Question 55

A light ray meets a plane mirror at 60 degrees. What is the angle of reflection?

Answer 55

60 degrees

Question 56

A light ray passes from air into water at an angle of 30 degrees. Give an example of an angle likely to be the angle of refraction.

Answer 56

22 degrees ray will bend towards the normal as it is going from a less dense to a more dense medium, meaning the angle of refraction will be smaller than the angle of incidence