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Physics Extension > Topic 1 - Radiation And Treatment > Flashcards

Topic 1 - Radiation And Treatment Flashcards

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1
Q

What are X-rays

A

High energy EM waves that get absorbed by dense materials

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2
Q

Are X-rays ionising or non ionising

A

Ionising

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3
Q

What can X-ray photographs diagnose

A

Bone fractures

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4
Q

What does CAT scans stand for

A

Computerised axial tomography

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5
Q

What do CAT scans produce

A

2D slice through the body

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6
Q

What do CAT scans use

A

Intense beams of X-rays

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7
Q

What can CAT scans do that x rays can’t

A

Image soft tissue as well as bones

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8
Q

What do endoscopes use to see inside the body

A

Optical fibres

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9
Q

What type of electromagnetic Ray do endoscopes use

A

Visible light

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10
Q

What do endoscopes help to reduce the use of

A

Invasive surgery

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11
Q

What frequency does ultrasound use

A

Above 20 kHz

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12
Q

What can ultrasound be used for

A

Breaking down kidney stones into sand like particles
Pre natal scan of a foetus
Measuring the speed of blood flow

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13
Q

What is radiation

A

Energy that originates from a source

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14
Q

What does the intensity of radiation depend on

A

Distance from a source

What it’s passing through

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15
Q

Unless passing through a vacuum some of the radiation will…..

A

Always be absorbed by the medium

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16
Q

Intensity equals

A

Power divided by area

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17
Q

Refraction is……

A

A change in direction caused by a change in speed

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18
Q

If a wave hits a boundary along the norm….

A

It will not change direction

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19
Q

What are the two main types of lenses

A

Converging and diverging

Or convex and concave

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20
Q

Convex lense cause light rays to…..

A

Converge to a focus at the lens focal point

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21
Q

Concave lens cause light rays to…

A

Spread out

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22
Q

The focal point of a diverging lens is the point where………

A

Rays hitting the lens parallel to the axis appear to come from

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23
Q

What are the three rules for refraction in a converging lens

A

An incident Ray parallel to the axis refracts through the lens and passes through the focal point on the other side

An incident Ray passing through the focal point before entering the lens will refract through the lens and travel parallel to the axis

An incident Ray passing through the centre of the lens will carry on in the same direction.

24
Q

At 2F the object will be……

A

Real, Inverted, same as object, at 2F

25
Q

An object between F and 2F will be….

A

Real, inverted, bigger than object, beyond 2F

26
Q

An object nearer than F will be

A

Virtual right way up, bigger than object and same side of the lens

27
Q

What are the three rules of a diverging lens

A

An incident Ray parallel to the axis refracts through the lens travels in line with the focal point
An incident Ray passing towards the focal point refracts through the lens and travels parallel to the axis
An incident Ray passing through the centre of the lens carries on in the same direction

28
Q

An diverging lens always produces….

A

A virtual image that is the right way up, smaller and on the same side of the lens

29
Q

The power of a converging lens is always

A

Positive

30
Q

The power of a diverging lens is always

A

Negative

31
Q

Power of lens equals

A

1 divided by focal length

32
Q

What does the iris do

A

Coloured part of the eye
Made up of muscles that control the size of the pupil
Controls how much light enters the eye

33
Q

What does the cornea do

A

The transparent window with a convex shape it does most of the eyes focusing

34
Q

How is light focused on by the retina

A

By the lens and the cornea working together

35
Q

What kind of power does the cornea have

A

Fixed

36
Q

What is the lens controlled by

A

Ciliary muscles

37
Q

What is the retina covered in

A

Light sensitive cells

38
Q

What is the furthest point your eye can see comfortable

A

Infinity

39
Q

What is the nearest point your eye can see

A

25cm

40
Q

Short sighted people cant…

A

Focus on objects that are far away

41
Q

What are x rays used for

A

Medical imaging

42
Q

Why are some people short sighted

A

Cornea and lens too powerful or eyeball is too long

Ciliary muscles can’t relax enough

43
Q

What can’t long sighted people do

A

Can’t focus on things close up

44
Q

Why are some people long sighted

A

Cornea or lens too weak
Eyeball is too short
Ciliary muscles can’t contract enough

45
Q

In long sighted people the I shed of near object are….

A

Brought into focus behind the retina

46
Q

How do you fix short sightedness

A

Diverging or concave lens

Brought into focus on the retina

47
Q

How can you correct long sightedness

A

Convex lens

Brought into focus earlier

48
Q

How else can you fix a vision defect

A

Contact lenses which compensate the fault of the eye shape

Laser eye surgery which permanently changed the shape of the cornea

49
Q

What is Snells law

A

When an incident Ray passed into a material the angle of incidence angle of refraction and refractive index are related by this formula

n = sin i
————-
sin r

50
Q

What is the critical angle

A

90 degrees

51
Q

If the angle of incidence is less than the critical angle…..

A

Most of the light passes out but a little bit of it is internally reflected

52
Q

If the angle of incidence is equal to the critical angle

A

The emerging Ray comes out along the surface there’s quite a bit of reflection

53
Q

If the angle of incidence is greater than the critical angle then

A

No light comes out

Total internal reflection

54
Q

You can find critical angles using…

A

Snells law

55
Q

Nr is ……

A

The refractive index of the stuff the lights travelling towards

56
Q

Ni is

A

The refractive index of the material the light starts from

57
Q

How do optical fibres work

A

Carry visible lights and can be used in medical diagnosis and communications technology
Work because of total internal reflection light waves are reflected off the sides of a thin inner core of plastic or glass
Reflected repeatedly until it reaches the other end

Physics Extension (5 decks)

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