Light

Question 1

What are the three things that can happen when light waves encounter a substance?

Answer 1

When light waves encounter a substance, three things can happen:

1. Transmitted (light travels through a substance)
2. Reflected (light bounces off a substance)
3. Absorbed (light is trapped by a substance and converted into heat energy)

Question 2

Do white objects transmit, reflect or absorb light?

Answer 2

White objects reflect all wavelengths of light.

Question 3

Do black objects transmit, reflect or absorb light?

Answer 3

Black objects absorb all wavelengths of light.

Question 4

What is a mirror?

Answer 4

A mirror is an object with a smooth surface that allows reflection of light to produce a clear image.

Question 5

What are mirrors made of?

Answer 5

Mirrors usually consist of glass with a metallic coating which is on the back of the glass generally.

Question 6

Can mirrors have flat or curved surfaces?

Answer 6

Mirrors can have flat or curved surfaces.

Question 7

What surface does a plane mirror have?

Answer 7

A plane mirror has a reflective flat surface.

Question 8

What surface does a concave mirror have?

Answer 8

A concave mirror has a surface that curves inwards.

Question 9

What surface does a convex mirror have?

Answer 9

A convex mirror has a surface that curves outwards.

Question 10

What is specular reflection?

Answer 10

Specular reflection is responsible for the sharp, clear images seen in mirrors. The light is reflected off in a singular direction. The angle of reflection is equal to the angle of incidence.

Question 11

What is diffuse reflection?

Answer 11

Diffuse reflection sends light off in a variety of directions; it is scattered. This type of reflection produces a distorted image, or no image at all.

Question 11

What does ‘The Law of Reflection’ do?

Answer 11

When light is projected towards the surface of a mirror, the angle that is reflected at can be predicted by the law of reflection.

Question 11

What is the ‘Law of Reflection’?

Answer 11

The angle of incidence equals the angle of reflection.

Question 12

What are concave mirrors?

Answer 12

Concave mirrors (converging mirrors) cause parallel light rays to converge (come together) after they reflect off the mirror.

Question 12

How do objects appear in a plane mirror?

Answer 12

The image in a plane mirror is exactly the same size as the object in front of it and is located exactly the same distance behind the mirror as the object is in front of it.

Question 13

What are convex mirrors?

Answer 13

Light rays that reflect off a convex mirror (diverging mirror) move away from each other - they diverge.

Question 14

How do concave mirrors reflect images differently depending on the distance between the object and the mirror?

Answer 14

When very close to an object, concave mirrors reflect images that are upright and larger (enlarged).

When far away from an object, concave mirrors reflect images that are inverted and smaller (diminished).

Question 15

Images formed by convex mirrors are:

Answer 15

1. Virtual (on the other side of the mirror)
2. Upright
3. Smaller: Size depends on how close the object is to the mirror.

Question 16

Images formed by a plane mirror are always:

Answer 16

1. Virtual (rays do not come from the image. The image is on the opposite side of the mirror relative to the object)
2. Upright
3. Same size
4. Same shape
5. As far behind the mirror as the object is in front of it.
6. Laterally inverted

Question 17

What is refraction?

Answer 17

Light rays may bend as they cross a boundary from one material to another, like from air to water. This bending of light rays is known as refraction.

Question 18

Which way does light bend when it refracts?

Answer 18

When light enters a new medium at an angle:
- If it goes from a less dense medium to a more dense medium, it will bend toward the normal. Light slows down.
- If it goes from a more dense medium to a less dense medium, it will bend away from the normal. Light speeds up.

Question 19

What is the ‘Index of Refraction’?

Answer 19

The degree that light bends when it enters a new medium is called the ‘Index of Refraction’.

Question 20

What is a converging lens?

Answer 20

A converging lens (or convex lens) is curved on both sides. This means the light rays coming out of it come together at a point - they converge.

Question 21

What is a biconcave lens?

Answer 21

A biconcave lens (diverging lens) has two inward curved surfaces.

Question 22

What do vision problems involve?

Answer 22

Vision problems involve the lenses being unable to focus on near or far objects.

Question 23

What is short-sightedness?

Answer 23

Short-sightedness (myopia) is a condition where people can see close objects clearly but distant objects appear blurry.

Question 24

Where is the focal point for short-sightedness?

Answer 24

The focal point is in front of the retina.

Question 25

How can you correct short-sightedness?

Answer 25

Using a concave lens (diverging lens) will move the focal point further away from the lens so that it falls on the retina.

Question 26

What is another name for short-sightedness?

Answer 26

Myopia

Question 27

What is far-sightedness?

Answer 27

Far-sightedness (hyperopia) is a condition where people can see distant objects clearly but objects close up appear blurry.

Question 28

Where is the focal point for far-sightedness?

Answer 28

The focal point is in behind the retina.

Question 29

How can you correct far-sightedness?

Answer 29

Using a convex lens (converging lens) will move the focal point closer to the lens so that it falls on the retina.

Question 30

What is the Vitreous Humour?

Answer 30

This fluid helps the eye hold its ‘spherical’ shape. The pressure of the vitreous humour helps to keep the retina in place.

Question 31

What is the cornea?

Answer 31

Thin clear mucous membrane that covers the front and inner surface of the upper and lower eyelids and makes eye movement and blinking easier.

Question 32

What is the pupil?

Answer 32

Dark space in the middle of the iris that enlarges and constricts depending on the brightness of light.

Question 33

What is the lens?

Answer 33

Clear capsule found behind the iris that bends the light rays entering the eye, forming a clear image on the retina. The fibres that hold the lens in place can change the lens shape. This is how the eyes can focus on objects at different distances.

Question 34

What is the iris?

Answer 34

The coloured part of the eye with the pupil at the centre. It is a muscle that can adjust the pupil size so light can enter, forming a retinal image.

Question 35

What is the retina?

Answer 35

Lining inside the back of the eye that contains light-sensitive receptors. These rods and cones are where images are formed from the light rays entering the eye and convert them into electrical impulses.

Question 36

What is the sclera?

Answer 36

The outer layer of the eyeball is made of tough interwoven fibres. Muscles attach to it, allowing eye movement.

Question 37

What is the optic nerve?

Answer 37

Nerve fibres that connect the retina and the brain. The optic nerve sends electrical impulses from the retina to the brain’s visual cortex. The image the brain receives is upside down, and the brain turns it up the right way.