Chapter 7

Question 1

What are the features of light?

Answer 1

1. Light is a form of radiation.
2. Light travels in straight lines.
3. Light transfers energy.
4. Light travels as a wave.
5. Light can travel through empty space.
6. Light is the fastest thing there is. (speed of light, universal speed limit)

Question 2

What are the laws of reflection?

Answer 2

1. The angle of incidence is equal to the angle of reflection.
2. The incident ray, the reflected ray, and the normal all lie in the same plane.

Question 3

Draw a reflection in a plane mirror.

Answer 3

Was it to his satisfaction?

Question 4

What happens to writing when shown through a mirror.

Answer 4

It gets laterally inverted (back to front)

Question 5

What is parallax?

Answer 5

It is the relative movement of an object viewed from two different lines of sight.

Question 6

Rules for Image size and position.

Answer 6

When a plane mirror forms an image. The image is the same size as the object, the image is as far behind the mirror as the object is in front, the line joining the equivalent points on the object and the image passes through the mirror at right angles. (perpendicular)

Question 7

Draw diagram of ray of light passing through a glass block. Include all angles and necessary lines.

Answer 7

get gud

Question 8

Angle of incidence definition.

Answer 8

this is the angle between the incident ray and the normal.

Question 9

Angle of refraction definition.

Answer 9

This is the angle between the refracted ray and the normal.

Question 10

What is the refractive index?

Answer 10

Speed of light in a vacuum divided by speed of light in the medium.

Question 11

What does a high refractive index mean?

Answer 11

The higher the refractive index the greater the bending effect.

Question 12

What is total internal reflection?

Answer 12

Total internal reflection happens past the critical angle. This is when all light is reflected and NO light is refracted.

Question 13

What happens to the refracted ray at the critical angle.

Answer 13

it travels along the border between the two mediums.

Question 14

What are examples of instruments that use internal reflection.

Answer 14

The periscope, optical fibers and rear reflectors.

Question 15

What’s the difference between Convex and Concave lenses?

Answer 15

Convex lenses converge the light rays that travel through it while Concave lenses diverge them.

Question 16

What physical characteristics do Convex and Concave lenses have?

Answer 16

Convex lenses are thicker towards the middle and thin around the edges. While Concave have thicker edges and a thinner middle.

Question 17

In a ray diagram, how many rays are needed to be able to find out where the image is projected?

Answer 17

At least two.

Question 18

In a ray diagram, when an object moves towards the lens, what effect does that have on the image of the object?

Answer 18

It gets larger and further away. (always going to be inverted)

Question 19

What is the formula for the critical angle?

Answer 19

Sin c = 1 / n (n is refractive index)

Question 20

What effect does a smaller refractive index have on the critical angle?

Answer 20

The smaller the refractive index, the bigger the critical angle.

Question 21

What is the principal focus of a Convex and Concave lens.

Answer 21

Convex: Where all the straight light rays converge after the lens
Concave: Where all the diverging light rays originate from behind the lens.

Question 22

How do you measure the focal length of a convex lens?

Answer 22

Choose an object in the distance, move convex lens either further away or closer until the object is sharp and focused on a blank screen. The distance between the image of the screen and the lens is the focal length.

Question 23

What is linear magnification?

Answer 23

Image height / object height = image distance / object distance (this is linear magnification)

Question 24

Features of images formed by convex lens

Answer 24

The image will be true to life and inverted. Depending on the position of the object relative to the focal point, the image will be smaller or bigger than the object.

Question 25

Using a convex lens, at what point will a real image (behind the focal point) be the same size as the original object?

Answer 25

When the focal length is half the distance of the object.

Question 26

For convex lenses, when will an image be virtual?

Answer 26

When the object is placed between the focal point and the lens.

Question 27

Of what parts does a camera consist of?

Answer 27

1. a lens that moves in our out to make focusing adjustments.
2. a shutter that opens and shut quickly to let a small amount of light into the camera
3. a film that is covered in light sensitive chemicals, when the film is exposed to light, different shades and colors form an image. Digital camera’s have a CCD instead of a film. (charged couple device)
4. the diaphragm controls the aperture of the hole through which the light passes.

Question 28

Of what parts does a projector consist of?

Answer 28

1. the projection lens forms the image on the screen, it has to be a long way from the screen in order to get a large image.
2. The film or LCD. Has to be inverted to give an upright picture on the screen.
3. The condenser lens concentrates light on the film or LCD so that it is very bright and evenly lit.

Question 29

What is an enlarger?

Answer 29

An enlarger is used when photographic prints are being made.

Question 30

If an object is brought closer to a camera, does the lens have to be moved further away from the film or closer>

Answer 30

Further away.’

Question 31

What does the condenser lens do?

Answer 31

It concentrates light on the film or LDC so it is very bright and evenly lit.

Question 32

How do light rays from a distant point converge?

Answer 32

Because the rays are effectively parallel to the lens. The majority of the rays converge at the principal focus.

Question 33

How do light rays from a close point converge?

Answer 33

If the rays come from a closer point and the lens make them converge closer from it

Question 34

What effect does a thicker convex lens have on the focal point?

Answer 34

If a thicker lens is used, the focal point is shorter (closer to the lens)

Question 35

What makes up the human eye?

Answer 35

1. The cornea does most of the converging.
2. The lens is used to make focusing adjustments called accommodation
3. The iris controls the amount of light entering the eye
4. The retina is the screen in the back of the eye where the image is formed.

Question 36

How can you correct short sight?

Answer 36

You can use a concave lens that diverges the light slightly before it enters the eye.

Question 37

How do you correct long sight?

Answer 37

You can use a convex lens in order to converge the light rays that enter the eye.

Question 38

How do electromagnetic waves form and where do they come from?

Answer 38

They are emitted whenever charged particles oscillate or lose energy in any way. (nucleus and electrons)

Question 39

What electromagnetic radiation is radiated from a glowing bulb filament

Answer 39

regular light and infrared

Question 40

How do radio waves reach cities / towns that are surrounded by mountains?

Answer 40

They can diffract around the hill/mountain

Question 41

Why do VHF and UHF waves (radio) are sometimes distorted.

Answer 41

because these waves don’t diffract around hills or obstacles.

Question 42

How do fluorescent lamps work?

Answer 42

The inside of a tube is coated with white power that absorbs ultraviolet radiation. The ultraviolet radiation is produced by passing the electric current through the gas.