Light

Question 1

Absorb - .

.

Answer 1

To ‘soak up’ or ‘take in’. If something absorbs light it soaks it up and does not let it back out

Question 2

Opaque -

Answer 2

Material that does not let light through.

Question 3

Reflect -

Answer 3

To bounce off something

Question 4

Translucent

Answer 4

• Material through which a glow of light can be seen. These materials scatter light, so a clear image cannot be seen.

Question 5

Transmit

Answer 5

To send along or pass through

Question 6

Transparent

Answer 6

-.
- Material that light can travel through and a clear image can be seen through it.

Question 7

Draw a ray diagram showing how a pin hole camera works

Answer 7

Question 8

What does the term inverted mean? Relate this to the image formed on the screen by the camera.

Answer 8

The image formed on the screen of the pinhole camera is inverted, which means it is upside down.

Question 9

*Explain why the pinhole camera produces an inverted image

Answer 9

Light can only go in straight lines. Light from the top of the object cannot go to the top of the screen because the case of the camera is opaque, so it blocks the light from reaching the screen. The only way light from the top of the object can reach the screen is to go diagonally through the hole, which results in the light reaching the bottom of the screen. Light from the bottom of the object can only reach the screen by going diagonally through the hole, arriving at the top of the screen.

Question 10

Explain how the image size can be changed.
How can you make it taller?

Answer 10

Taller – use a taller object, move the object closer to the camera. The light from the top and the bottom of the image will spread out further before reaching the screen.

Question 11

Explain how the image size can be changed. How can you make it shorter?

Answer 11

Smaller – shorter object, move object further from the camera. The rays from the top and the bottom of the object will become less spread out when the arrive at the screen

Question 12

*Compare and contrast the image produced by a pinhole camera with a small hole and a pinhole camera with a large hole. Explain any differences.

Answer 12

Large hole image brighter by more blurred. Small hole image dimmer by in sharper focus. Large hole lets in more light than the small hole, hence a brighter image. A small hole restricts how much light can enter, whereas the large hole lets in more light, not all of which is brought to a focus at the same place, hence the blurred image.

Question 13

What is the law of reflection?

Answer 13

Law of reflection is:
angle of incidence = angle of reflection

Question 14

What is the nature of the image formed by a plane mirror?

Answer 14

Question 15

What is refraction?

Answer 15

Light is refracted when it reaches the boundary between two transparent materials.
When light is refracted it changes direction.
Going from air into glass bends towards the normal.
Going out of glass into air bends away from the normal.
When travelling along the normal light does not change direction
Refraction occurs because the waves change speed

Question 16

Why does refraction happen?

Answer 16

Because light changes speed when it enters a material of a different density

Question 17

What effect does a prism have on white light?

Answer 17

White light is a mixture of many different colours, each with a different frequency.
White light can be split up into a spectrum of these colours using a prism, a triangular block of glass or Perspex.
Light is refracted when it enters the prism, and each colour is refracted by a different amount.
This means that the light leaving the prism is spread out into its different colours, a process called dispersion.

Question 18

Explain why the green writing disappeared when viewed under a green light.

Answer 18

The green light is reflected by the green writing because it can only reflect green light. The white parts of the page can reflect any colour, so it reflects the green light. If both the writing and the page reflect green light you will not be able to see where the writing is on the page, hence the writing disappears.

Question 19

Explain why the green writing appeared black when viewed under the red light.

Answer 19

The green writing absorbs the red light because it cannot reflect it. The absence of light been reflected is seen as black. The white parts of the page can reflect any colour, so it reflects the red light.

Question 20

Describe and explain what would be seen if you wore a white shirt and a green and blue stripy tie to a disco and stood under a blue light

Answer 20

White shirt can reflect any colour, so reflects the blue light. Your eye receives blue light so you see the shirt as blue. The blue parts of the tie can only reflect blue light, whereas the green stripes cannot reflect blue light, they can only absorb blue light. Blue light is reflected to you eye from the blue stripes so you see them as blue, and the absence of any light reflected by the green parts is seen as black.

Question 21

Explain how a red filter works. Refer to the colours it absorbs and transmits. Illustrate your answer with a diagram

Answer 21

White light is made up of seven colours – red, orange, yellow, green, blue, indigo and violet. When the white light meets the red filter only the red light is transmitted. All the other six colours of white light are absorbed by the filter.

Question 22

What would you see if you put a blue filter in front of a green filter when looking at a white light? Draw a diagram to illustrate your answer

Answer 22

White light is made up of seven colours – red, orange, yellow, green, blue, indigo and violet. When the white light meets the green filter only the green light is transmitted. All the other six colours of white light are absorbed by the filter.
When the green light transmitted by the green filter meets the blue filter, the blue filter absorbs the green light. A blue filter can only transmit blue light.
In the absence of any light getting through the second filter you would see black.

Question 23

What colour would a blue jumper appear through a red filter and why? Draw a diagram to help explain your answer

Answer 23

White light is made up of seven colours – red, orange, yellow, green, blue, indigo and violet.
When the white light meets the blue jumper only the blue light is reflected, all the other colours of white light are absorbed.
When the blue light reflected form the jumper meets the red filter the blue light is absorbed because a red filter can only transmit red light.
In the absence of any light getting through the blue filter you would see black.

Question 24

Answer 24

When a polythene rod is rubbed by a cloth it becomes charged.
This is caused by the movement of electrons from the cloth to the rod.
When rubbed together friction causes some electrons on the cloth to be knocked off atoms.
These electrons stick to the atoms of the polythene rod.
As electrons have a negative charge (-) the polythene rod gains a negative charge.
As the cloth has lost the electrons negative charge (-) the cloth gains a positive charge