P14-Light

Question 1

What happens when plane waves reflect from a flat barrier?

Answer 1

The reflected waves are at the same angle to the barrier as the incident waves

Question 2

What happens when each point on the wave front teaches the barrier?

Answer 2

It creates a wavelet moving away from the barrier, the wavelet lines up with the previous reflected wavelets to form a reflected wave front moving away

Question 3

All parts of a wavefront move at the same speed. What does this mean?

Answer 3

the reflected wavefront is at the same angle to the barrier as the incident wavefront

Question 4

In reflection, the reflected and incident waves have the same what?

Answer 4

Frequency, speed and wavelength

Question 5

What do light rays show?

Answer 5

The direction that light waves are moving in

Question 6

The line perpendicular to the mirror is called the what?

Answer 6

the Normal

Question 7

What is the angle of incidence?

Answer 7

the angle between the incident ray and the normal

Question 8

What is the angle of reflection?

Answer 8

angle between reflected ray and the normal

Question 9

What is the image formed by a plane mirror?

Answer 9

virtual

Question 10

When is a virtual image formed?

Answer 10

When light rays appear to come from after they have been reflected or refracted

Question 11

What is a real image

Answer 11

An image that can be seen on a screen

Question 12

what is a virtual image?

Answer 12

1. same way up as the object

2. laterally inverted (back to front not upside down)

Question 13

What is specular reflection?

Answer 13

Diffusion from a smooth surface because parallel light waves are reflected in a single direction

Question 14

What can a virtual image not do?

Answer 14

be projected onto a screen like the movie images you see at a cinema

Question 15

Why may a real image be described as something seen on a screen?

Answer 15

A real image is formed by focusing light rays onto the screen

Question 16

What is reflection from a rough surface called why?

Answer 16

diffuse reflection- light is scattered in different directions

Question 17

Each lens changes the direction of light passing through it. What is this change of direction called?

Answer 17

refraction

Question 18

What is refraction?

Answer 18

The change in direction of waves across a boundary from one medium to another

Question 19

When do light waves refract?

Answer 19

When they travel across a boundary between air and a transparent medium.

Question 20

Why does light refract across a boundary between air and a transparent medium.?

Answer 20

This is because speed of light changes at this type of boundary

Question 21

What does light do when it travels from air to glass?

Answer 21

Bends towards the normal

Question 22

What does light do when it travels from glass to air?

Answer 22

Bends away from the normal

Question 23

What does light bend away from the normal when it travels from glass to air

Answer 23

Light travels more slowly in glass than air and glass is more optically dense than air

Question 24

What happens when light enters a more dense medium?

Answer 24

Refracted towards normal

Question 25

What happens when light enters a less dense medium?

Answer 25

Refracted away from medium

Question 26

How do colour filters work?

Answer 26

They absorb certain wavelengths and transmit others e.g. white light at red filter inky red light emitted because it absorbs all parts of white spectrum

Question 27

What are the primary colours of light? And why are they the primary colours?

Answer 27

Red, green and blue and because they can be mixed to produce any other colour of light

Question 28

What does the colour and surface of an opaque object depend on?

Answer 28

The chemicals (pigments) in the surface materials

Question 29

What does colour also depend upon?

Answer 29

The range of wavelengths in the incident light

Question 30

What does a white surface not have ?

Answer 30

Pigments

Question 31

What are transparent objects?

Answer 31

Objects that transmit all the incident light that hit object, none is absorbed

Question 32

What are translucent objects?

Answer 32

Objects that let light pass through but is scattered or refracted

Question 33

Why do translucent objects let light pass through but is scattered or refracted

Answer 33

Material of object has lots of internal boundaries that change the direction of the light waves

Question 34

What is another word for convex lens

Answer 34

converging

Question 35

What is a convex lens?

Answer 35

Makes parallel rays converge to a focus

Question 36

What is the point called where parallel rays are focused to?

Answer 36

Principal focus

Question 37

What is a converging lens used for?

Answer 37

Magnifying glass e.g. distant objects in a camera

Question 38

What is a concave lens used for?

Answer 38

Makes parallel rays spread out

Question 39

Whats another word for concave?

Answer 39

diverging

Question 40

What is a diverging lens used for?

Answer 40

Correcting short sight

Question 41

What is the distance from the centre of the lens to the principle focus called?

Answer 41

Focal length

Question 42

What happens if the image is bigger than the object?

Answer 42

The magnification is bigger than 1

Question 43

What happens if the image is smaller than the object?

Answer 43

The magnification is less than 1

Question 44

What image is formed by a convex lens?

Answer 44

A real image if the object is further away than the principal focus

Question 45

What image is formed by a convex lens?

Answer 45

A virtual image if object is nearer the principal focus

Question 46

The magnification produced by a lens is what formula?

Answer 46

image height over object height