P14-Light

Question 1

The Law of reflection

Answer 1

Angle of incidence = angle of reflection

Question 2

What is a virtual image?

Answer 2

The image formed by a plane mirror. It is formed at a place where light rays appear to come from after they have been reflected.

Question 3

What is specular reflection?

Answer 3

Reflection from a smooth surface. The parallel light rays are reflected in a single direction.

Question 4

What is diffuse reflection?

Answer 4

Reflection from a rough surface is called diffuse reflection because the light is scattered in different directions.

Question 5

Refraction in water waves

Answer 5

When they cross a boundary between deep and shallow water at a non-zero angle to the boundary. The change of speed at the boundary causes them to change direction.

Question 6

Direction when light travels from air into glass

Answer 6

Towards the normal line

Question 7

Direction when light travels from glass into air

Answer 7

Away from the normal line

Question 8

Difference in optical density between glass and air

Answer 8

Light travels more slowly in glass than in air

Question 9

Apart from refraction, what can happen when waves cross a boundary between two materials?

Answer 9

Partial reflection

Question 10

Transparent objects

Answer 10

Transmit all the incident light that enters the object. The transmitted light travels through the object

Question 11

Translucent objects

Answer 11

Let light pass through them, but the light is scattered or refracted

Question 12

Opaque objects

Answer 12

An object that absorbs all the light that reaches it.

Question 13

How do lenses work?

Answer 13

By changing the direction of light passing through it.

Question 14

Convex lens

Answer 14

Makes parallel rays converge to a focus

Question 15

What is the ‘principal focus’ or ‘focal point’?

Answer 15

The point where parallel rays are focused to .

Question 16

Uses of a convex (converging) lens

Answer 16

As a magnifying glass and in a camera to form a clear image of a distant object.

Question 17

Concave lens

Answer 17

Makes parallel rays diverge (spread out).

Question 18

What is the principal focus for a concave (diverging) lens?

Answer 18

The point where the rays appear to come from

Question 19

Uses of a Concave lens

Answer 19

To correct short sight

Question 20

What is the focal length ?

Answer 20

The distance from the centre of the lens to the principal focus

Question 21

Magnification Equation

Answer 21

Magnification = image height / object height

Question 22

If the object is at a distance beyond the principal focus of the lens what type of image is formed?

Answer 22

Real image

Question 23

If the object is nearer to the lens than the principal focus what type of image is formed?

Answer 23

A magnified, virtual image

Question 24

What happens if the object is between a concave lens and its principal focus?

Answer 24

The image is virtual, upright and larger than the object.

Question 25

What happens to the image created if the object is beyond thr principal focus pf the lens?

Answer 25

The image is real, inverted and smaller than the object

Question 26

Reflection RP (method)

Answer 26

1. Place a plane mirror on a sheet of paper
2. Draw a line 90 degrees (perpendicular) to the mirror
3. Measure a chosen angle with a protractor and mark it
4. Turn on a ray box with slits and shine a light ray at the mirror through the marking
5. The light ray that is reflected can be measure with a protractor and it will be equal to the incident light ray

Question 27

Refraction RP (method)

Answer 27

1. Place a perspex block on a sheet of paper
2. Draw around it with a pencil
3. Using a ray box shine a light ray towards the block at a specific angle(using a protractor)
4. Mark the point where the ray enters and leaves the block and continue this point for 5cm
5. Remove the block and draw a dashed normal line to the points outside the block
6. Measure the angle of refraction