commonly asked qns

Question 1

state the two laws of reflection

Answer 1

1. the angle of incidence and the angle of reflection is equal
2. the incident ray, the reflected ray and the normal lie on the same plane

Question 2

why does object B appear to be nearer to the surface of water than it actually is?

Answer 2

When light ray travels from water to air, the light ray bends away from the normal as light ray is travelling from an optically denser medium to an optically less dense medium. hence when light rays from object B come out, they are bend. However, our brain thinks that the light ray travels in a straight line, so B appears to be at a higher position than it actually is.

Question 3

explain why light bends when it travels from one medium to another medium

Answer 3

light bends because it’s speed changes when it moved from one transparent medium to another

Question 4

name the characteristics of the image formed by a plane mirror

Answer 4

1. laterally inverted
2. upright
3. virtual
4. same size
5. equal distance from object to mirror to mirror to image

Question 5

characteristics of image formed by convex mirror

Answer 5

1. upright
2. virtual
3. diminished

Question 6

characteristics of image formed by concave mirror

Answer 6

• virtual
• upright
• magnified

Question 7

what is dispersion of light

Answer 7

dispersion is the splitting of white light into it’s component colours

Question 8

why does white light split into a spectrum of colours when it passes through a prism

Answer 8

when white light enters a prism, it slows down because the prism is denser than air, hence the different colours of white light bend towards the normal through different angles when entering and leaving the prism, thus white light splits into a spectrum of colours

Question 9

uses of plane mirrors

Answer 9

• mirror in dance studios
• mirror used for eye charts
• periscopes

Question 10

uses of convex mirror

Answer 10

convex mirror is used when a wide field of view is needed

• side view mirror of cars
• rear view mirror of cars
• security mirrors
• blind spot mirrors

Question 11

uses of concave mirrors

Answer 11

concave mirrors are used when a magnified image is needed

• cosmetic mirrors
• dentist mirrors
• mirrors behind car’s headlights

Question 12

what is reflection

Answer 12

reflection is the bouncing off light rays incidence on a smooth, reflective surface which angle is equal to angle of incidence. the light rays reflect in the same direction, this is called regular reflection

Question 13

what if light is reflected on a rough surface?

Answer 13

light rays are incidence on rough surfaces, hence the rays will be reflected in different directions, depending on the surface it’s reflects off, this is called diffused reflection

Question 14

explain what are convergent beams

Answer 14

convergent beams are groups of light rays which emerge from different directions, focuses and meet at a point

Question 15

explain what divergent beams are

Answer 15

divergent beams are light rays that emerge from a point source of light, spread and travel in all directions, moving away at the same time

Question 16

explain what parallel beams are

Answer 16

parallel beams are a group of light rays from a distant point source which travel parallel to each other in a particular direction

Question 17

what is a virtual image

Answer 17

it is an image that cannot be captured on a screen