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Physics > Chapter 9 - Light > Flashcards

Chapter 9 - Light Flashcards

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1
Q

Draw the diagram to show how we see a object in a mirror.

A

Do it it’s very important

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2
Q

What are the features of an image in a mirror ?

A
  • virtual
  • the same size as the object
  • laterally inverted
  • the same distance behind the mirror as in front of the mirror
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3
Q

What is the speed of light in air (or vacuum) , water and glass ?

A

Air (or vacuum) : 3 x 10^8
Water: 2.25 x 10^8
Glass: 2 x 10^8

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4
Q

What is the definition of refraction ?

A

Where a (light) wave passes from one material into another and change in the wave speed results in a change in wave speed

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5
Q

What is the angle between the incident ray and the normal called ?

A

angle of incedence

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6
Q

What is the angle between the normal and the refracted ray called ?

A

angle of refraction

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7
Q

What is the angle between the emergent ray and the normal called ?

A

angle of emergence

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8
Q

When light speeds up which way does it bend ?

A

Away from the normal

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9
Q

When light slows down which way does it bend ?

A

Towards the normal

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10
Q

What are the colours of the spectrum in order of fastest to slowest ?

A 
Fastest: red
orange
yellow
green
blue
indigo 
Slowest: violet
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11
Q

What is dispersion ?

A

When light is passed through a triangular glass block, the effect called dispersion and you can see a spectrum of all the colours of the rainbow

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12
Q

What is the critical angle ?

A

The critical angle is the angle of incidence in a material for which the angle of refraction in air is 90*

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13
Q

What happens at angles of incidence less than the critical angle ?

A

at angles of incidence les than the critical angle, both reflection and refraction occur

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14
Q

What happens at angles of incidence greater than the critical angle ?

A

at angles greater than the critical angle , no refraction occurs and the light is totally internally reflected

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15
Q

When does total internal reflection occur in parallel-sided glass blocks ?

A

At angles of incidence above the critical angle

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16
Q

Why is monochromatic light used ?

A

it is used to avoid unwanted dispersion

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17
Q

Read page 119 in text book

A

Hard to write fc for so

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18
Q

What are optical fibres ?

A

optical fibres are lengths of solid glass core with an outer plastic sheath

19
Q

What are optical fibres used for ?

A

To transmit both telephone and video signals over long distances

20
Q

Why are optical fibres so good ?

A

They can carry much more information than a copper wire of the same diameter

21
Q

What is one use of optical fibres in medicine ?

A

Endoscope are made up of optical fibres and allow the doctor to look inside the patients body. They allow light to travel into the body and allow image info to be passed back out.

22
Q

What are the two main types of lens ?

A

Converging and diverging

23
Q

Draw a converging lens

A

Fatter one

24
Q

Draw a diverging lens

A

Thinner one

25
Q

What are the two features of a converging lens ?

A
  • Rays of light parallel to the principal axis of a converging lens all converge to the same point on the other side of the lens
  • This point is called the principal focus
26
Q

What are the two features of a diverging lens ?

A
  • Rays of light parallel to the principal axis of a diverging lens all appear to diverge from the same point after refraction in the lens
  • This point lies on the principal axis, and is called the principal focus
27
Q

What is the definition of focal length ?

A

The distance between the principal focus and the optical centre, C, of any lens is called the focal length

28
Q

Look at page 126 and draw the ray diagrams

A

DO IT PLEASE.

29
Q

Where does most refraction of light occur in the eye ?

A

The cornea

30
Q

What is the purpose of the lens in the eye ?

A

To produce a sharp image on the retina

31
Q

What is the optical nerve ?

A

How nerve endings pass messages to the brain

32
Q

What is the far point ?

A

The farthest point hat can be seen clearly by the eye is called the far point

33
Q

How long is the far point for the eye ?

A

infinity

34
Q

How does light from afar reach the eye ?

A

Light rays from a far reaches the eye as parallel rays. The rays are refracted by the cornea and lens so the image is sharp on the retina.

35
Q

What is the near point ?

A

The nearest point that can be seen clearly with the unaided eye without causing muscles to strain is called the near point.

36
Q

How long is the near point ?

A

About 25cm

37
Q

How does light get to the eye from the near point ?

A

The light reaches the eye from the near point as diverging rays.

38
Q

What is another name for short sightedness ?

A

myopia

39
Q

What are people with myopia unable to do ?

A

They cannot make the lens thin enough to view distant objects. This causes the light to converge just in front of the retina making the image blurry.

40
Q

How do you correct myopia ?

A

A diverging lens is used. The light diverges just before just before the eye. The lens and the cornea can then bring these diverging rays to a shar focus on the retina.

41
Q

What is the other name for long sightedness ?

A

hypermetropia

42
Q

What can a person with hypermetropia not do ?

A

Their eye muscles are not strong enough to make the lens thick enough for the light to form a sharp object

43
Q

How do you correct hypermetropia ?

A

Use a converging lens. This light is now less diverging then before. The cornea and the eye lens can now bend the light so that a sharp image is formed on the retina

Physics (18 decks)

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