P14 - Light

Question 1

What is reflection

Answer 1

When a wave hits a boundary/surface and instead of travelling to the new medium, it bounces back

Question 2

What is the normal line

Answer 2

The line perpendicular to the surface/ boundary (plane)

Question 3

Angle of incidence = _______?

Law of Reflection

Answer 3

Angle of incidence = angle of reflection

The incidence and reflected rays also have the same frequency, speed and wavelength

Question 4

What is specular reflection

Answer 4

Reflection from a smooth surface where all of the reflected light rays go in one direction
Specular reflection produces an image

Question 5

What is diffuse reflection

Answer 5

Reflection from a rough surface where the reflected light rays are scattered in different directions
Diffuse reflection doesn’t produce an image

Question 6

What is a virtual image

Answer 6

The image from which light rays appear to be coming from

Question 7

Describe the image formed by a plane mirror

Answer 7

Virtual, upright and laterally inverted

Question 8

Defenition of Refraction

Answer 8

The change in direction of a light ray as it passes the boundary between two different transparent substances

Question 9

How do colour filters work?

Answer 9

They absorb certain colours and transmit others e.g. white light on a red filter only transmits red light

Question 10

Primary colous of light

Answer 10

Red, green, blue

Question 11

Secondary colours of light

Answer 11

Cyan, Yellow, Magenta

Question 12

What colour would a red object look like through a blue filter

Answer 12

Black as all colours would be absorbed

Question 13

Why does an object have a certain colour e.g. a red apple

Answer 13

The apple absorbs all other colours and only reflects the red

Question 14

Defenition of transparent object

Answer 14

An object that transmits all the light that enters it

Question 15

Defenition of a translucent object

Answer 15

An object that tramsits all the light, but it is refracted in the process

Question 16

Defenition of an opaque object

Answer 16

An object that doesn’t trasmit any light. All the light is either scattered, reflected or absorbed

Question 17

What is a convex lens and what do they do

Answer 17

• A lens that is thicker at the centre than it is at the edges
• It is shown by a line with outwards facing arrows
• They converge parallel light rays to a principal focus point and the distance from the centre of the lens to the focal point is the focal length
• The centre light ray doesn’t get refracted as it is passing along the normal (the principal axis

Question 18

What is a concave lens and what do they do

Answer 18

• A lens that is thicker at the edges than at the centre
• It is shown by a line with inwards facing arrows
• They diverge parallel light rays so the principal focus is behind the lens where the light rays came from - the light rays only appear to be coming from this point

Question 19

Will the image formed by a convex lens be real or virtual

Answer 19

It can be either

Question 20

Will the image formed by a concave lens be real or virtual

Answer 20

Always virtual

Question 21

Describe the image formed by a concave lens

Answer 21

It will always be virtual, upright and diminished

Question 22

Describe the image formed by a convex lens when the object is more than 2 focal lengths away from the lens

Answer 22

Real, inverted and diminished

Question 23

Describe the image formed by a convex lens when the object is between 1 and 2 focal lengths away from the lens

Answer 23

Real, inverted and enlarged

Question 24

Describe the image formed by a convex lens when the object is inside its focal point

Answer 24

Virtual, upright and enlarged

Question 25

Colours in the light spectrum

Answer 25

• Red, orange, yellow, green, blue, indigo and violet
• On the left is red which has a lower frequency and longer wavelength and on the right is violet which has a higher freqeuncy and a shorter wavelength

Question 26

Equation for magnification

Answer 26

magnification = image height/object height

magnfication doensn’t have units as it is a ratio