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Science Yr8 > Light Waves Doddle > Flashcards

Light Waves Doddle Flashcards

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1
Q

What is light?

A

Light is produced by the sun and other luminous objects such as light bulbs and matches. We can see non-luminous sources because light bounces off them and enters our eyes.

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2
Q

What speed does light travel and how does it travel?

A

Light travels at the speed of 300,000,000 metres per second, which is too fast for us to see it travel. Light travels in straight lines, shadows are made because light cannot travel through objects. Light is a wave that carries energy.

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3
Q

Waves in a Vacuum

A

Matter waves need a medium in which to travel. Light waves on the other hand do no need. A medium transfer energy. This absence of a medium is called a vacuum. Space is a vacuum and light can travel through it this is why we can see light from distant stars.

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4
Q

What happens when light is transmitted?

A

If light passes through an object it’s transmitted. If light is transmitted and also changes its direction it is refracted. The new direction of the light depends on the material. Transparent materials like glass allow light to travel through them, translucent objects allow some light to travel through the. Opaque objects block light from travelling through them forming a shadow.

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5
Q

What happens when light is absorbed?

A

Some materials absorb light, transforming the energy into heat. Dark objects absorb more light than pale ones.

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6
Q

What happens when light is reflected?

A

If light bounces of an object is reflected.

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7
Q

What are some qualities of an object that reflects well?

A
  • Smooth, shiny surfaces and are usually pale colours

- Give clear images because they reflect light regularly. This is called secular reflection

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8
Q

What are some qualities soft objects that do not reflect light well

A
  • rough, matt surfaces and are usually dark colours

- do not give a good image because they reflect light irregularly. This is called scattering.

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9
Q

What are the qualities of a plane mirror?

A
  • a plane mirror is a flat and shiny mirror that reflects light regularly so it produces a clear image
  • it is made with glass or silver on the back
  • the image appears the same distance behind the mirror as it is in front of it and the image is the same size as the object
  • when an object is reflected in a plane mirror left appears as right and right appears as left. This type of reversal is called lateral inversion.
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10
Q

What is the normal?

A

The normal is a line that is drawn at right angles to the mirror. It helps us to measure the angles

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11
Q

What is the angle of incidence?

A

The angle of incidence is the angle between the incident ray and the normal

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12
Q

What is the angle of reflection?

A

The angle of reflection is the angle between the incident ray and the normal

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13
Q

What is the reflected ray?

A

The ray of light that comes away from the mirror is the reflected ray

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14
Q

What is the incident ray?

A

The ray of light that goes towards the mirror is the incident ray

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15
Q

What is relationship between the angle of reflection and the angle of incidence on a plane mirror?

A

The angle of incidence is equal to the angle of reflection on a plane mirror

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16
Q

What is refraction?

A

Refraction is when light travels from one substance to another. It changes direction. This is called refraction. This happens at the boundary between substances.

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17
Q

Give some examples of refraction:

A
  • it’s hard to judge where a fish is when it is underwater because the light bends as it moves from water into air. People who are fishing with spears must aim behind the fish’s image to compensate for this.
  • a straw looks different from how it looks in the air. The light bends at the air-glass, water-glass and air-water boundaries producing a distorted image
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18
Q

What is the angle of refraction.

A

The angle of refraction is the angle between the refracted ray and the normal ray

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19
Q

How do you know the speed of light?

A

The speed of light depends on the material the light is travelling through. When light enters a different material (e.g. when moving from air into glass), the speed of light changes. This causes the light to bend or refract.
The speed of light is affected by the density of the material it is travelling through. When light enters a more dense medium, its speed decreases and this is why refraction occurs.

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20
Q

What happens during refraction (air-glass)?

A

-light travelling from air into glass is bent towards the normal. In general, when light enters a more dense medium it is refracted towards the normal. This means that the angle of incidence is greater than the angle of refraction as the refracted ray is bent towards the normal.

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21
Q

What happens during refraction (glass-air)?

A

-light travelling glass into air is bent away from the normal. In general, when light enters a less dense medium it is refracted away from the normal. This means that the angle of incidence is less than the angle of refraction.

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22
Q

What happens when the angle of incidence is 0°

A

When an angle of incidence at an air-glass boundary is 0°, te light ray does not deviate from its straight line

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23
Q

Describe lenses:

A

Lenses are made from transparent materials and have curved surfaces.

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24
Q

Describe convex lines:

A

Convex lines are thicker in the middle than at the edges. The refract light rays into a single focusing point. Convex lenses occur naturally in the eye. They are used in camera lenses, in spectacles and magnifying glasses.

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25
Q

Describe concave lenses:

A

Concave lenses are thinner in the middle than at the edges. They make parallel light rays diverge.

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26
Q

Describe images produced by convex lenses:

A

Convex lenses produce different types of images depending on how far away the object is from the lens. This is easily demonstrates with a magnifying lens.

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27
Q

How do our eyes detect light?

A
  • Light from a source travels to the eye or light reflected of an object travels to the eye
  • the light passes through the cornea and pupil and enters the eye. The cornea refracts the light rays
  • the light now passes through the lens which refracts the light even more. This is how the eye focuses the light
  • finally, the light rays hit the back of the retina. The receptors can now detect a light and send a message along the optic nerve to the brain.
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28
Q

The eyes recording light -retina

A
  • at the back of they eye there is a layer of photosensitive (which means responds to light) material called the retina
  • the retina has millions of photoreceptors (photoreceptors are photosensitive) that react to light and recognise movement and different colours. The retina has a similar function to the film in a camera. It captures and converts light into electrical signals that are sent to the brain by the optic nerve. The brain then translates the electrical signals into the images we see.
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29
Q

What is the size of the pupil controlled by?

A

The iris

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30
Q

Qualities of the pinhole camera:

A

The pinhole camera is the simplest kind of camera. It is made of a light-proof box that doesn’t let in light with a single small pinhole on one side and a screen on the other.
Light rays are reflected from an object and pass through the pinhole to project a crisp inverted image on the screen.
The pinhole acts as a lens and can be made bigger or smaller to control how much light enters the box.
The image is upside down.

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31
Q

Where does the word photo come from?

A

Photo comes from the Greek word for light

32
Q

The camera - recording light

A

The camera is used to record images into film. The film is plastic coated with tiny light-sensitive grains.
When photographic film is exposed to light the grains undergo a chemical reaction. The result is a record of the pattern of light on the film.
The film is developed by exposing it to other chemicals to produce a representation (a print) of the original image.

33
Q

Splitting white light:

A

A prism splits a ray of white light into the colours of the rainbow.
This process is known as dispersion.

34
Q

What are the colours that make up white light called?

A

The spectrum

35
Q

Why does dispersion occur?

A

Dispersion occurs because different colours of light refract differently. Red light refracts the least; violet the most

36
Q

What is the order of colours in the spectrum?

A

Red, orange, yellow, green, blue, indigo and violet

37
Q

Why does dispersion in a prism occur?

A

Dispersion in a prism occurs because different colours of light have different frequencies. The frequency of light is the number of waves that pass a certain point every second. The higher the frequency the more the light is slowed down and the more it is refracted by a prism. Red light has the lowest frequency and refracts the least and violet light has the highest frequency and refracts the most.

38
Q

Give an example of natural dispersion:

A

If there are water droplets in the air and the sun is illuminating the, from the air behind, then you may see a rainbow in the air.
Light enters the water droplets and refracts. It then reflects off the back of the raindrop.
The colours refract different amounts this causes dispersion.

39
Q

Recombining colours

A

When the spectrum made by the first prism passes through a second prism the colours are recombined to make white light again. This is known as recombination.

40
Q

What colour is made when red light and blue light mix?

A

Magenta light

41
Q

What colour is made when red light and green light mix?

A

Yellow

42
Q

What colour is made when green light and blue light is mixed?

A

Cyan

43
Q

Why does a red object look red in white light?

A

A red object absorbs all the colours of the spectrum except red. Only red light is reflected from the object into your eye so the objects appear red.

44
Q

Why does a green object look green in white light?

A

A green object absorbs all the colours of the spectrum except green. Only green light is reflected from the object into your eyes so the object appears green.

45
Q

Why does a magenta object look magenta in white light?

A

A magenta object absorbs all the colours of the spectrum except red and blue . Red and blue light are reflected of the object and into your eyes so the object appears magenta.

46
Q

Why does a black object look black in white?

A

A black object absorbs all the colours of the spectrum so no light is reflected off the object and into your eyes so the object appears black.

47
Q

Why does a white object look white in white light?

A

A white object does not absorb any of the colours of the spectrum. The whole spectrum is reflected into your eyes, so the object appears white.

48
Q

What colour does a red object appear in red light?

A

Red light shines on a red object but is not absorbed by it. The red object appears red light into your eye so it appears red.

49
Q

What colour does a red object look in red light?

A

Green light shines on the red object and is absorbed by it. The red object does not reflect any light into your eye so it appears black.

50
Q

What colour does a red object appear in magenta light?

A

Magenta light which is made up of red and blue light shines on the red object. The red object absorbs the blue light but reflects the red light into your eyes so it appears red.

51
Q

Absorption

A

When light is taken in by a material

52
Q

Dispersion

A

The separating of the colours in light e.g. when light passes through a prism

53
Q

Image

A

A copy of an object formed when light is reflected from a mirror

54
Q

Law of reflection

A

When light is reflected the angle of incidence equals the angle of reflection

55
Q

Light

A

A form of energy that is detected by the eyes

56
Q

Prism

A

A block of glass, usually triangular, which separates the coloured in light

57
Q

Reflection

A

The bouncing back of light from a surface

58
Q

Refraction

A

The bending of light when it passes into a different medium e.g, air into glass

59
Q

Spectrum

A

The range of colours that make up white light

60
Q

Does light travel faster than sound?

A

Yes, light travels are Lund 1,000,000 times faster than sound

61
Q

What is the speed of light in a vacuum?

A

The speed of light is 300,000km per second through a vacuum. This is the maximum speed at which all matter in the universe can travel

62
Q

What is light from the sun called?

A

White light

63
Q

Examples of refraction:

A
  • a rainbow
  • a fish that looks closer to a surface than it really is
  • a pencil that looks bent in a glass of water
64
Q

What is a narrow beam called?

A

A ray

65
Q

What is it called when waves get placed on top of each other?

A

Superposition

66
Q

What happens in superposition?

A

The waves can either cancel each other out or add up.

67
Q

Digital cameras:

A

Digital cameras have a grid of photosensitive elements, called pixels. The grid is called a charged-coupled device. When light hits each pixel, it produces an electrical song, which is stored in the cameras memory.

68
Q

How do we see an object that does not give out light.

A

We see the object because light hits it and it is reflected into our eyes

69
Q

Ciliary muscle

A

Controls the shape of the lens

70
Q

Iris

A

Controls the amount of light entering the eye

71
Q

Lens

A

Focuses light onto the retina

72
Q

Cornea

A

Focuses light and protects the eye from damage

73
Q

Retina

A

Where the focused light is detected

74
Q

Optic nerve

A

Carries information from the eye to the brain

75
Q

What are the colours that make up white light called?

A

The visible light spectrum

Science Yr8 (26 decks)

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