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Physics > P3.1 Medicle Physics > Flashcards

P3.1 Medicle Physics Flashcards

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0
Q

Proportions of x rays?

A

Short wavelength

Very ionising

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1
Q

What length are x-rays?

A

10^-10m

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2
Q

How does an x ray work?

A

It’s absorbed by more dense materials like bone and metal but is transmitted through soft tissue creating an imagine

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3
Q

Uses of x rays?

A

Diagnosis
Treatment
Plan treatment

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4
Q

How are x rays made?

A

An accelerating electron hits atoms in a heavy metal target which emits them

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5
Q

What precautions need to be taken with x rays?

A

DES

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6
Q

What are CT scans?

A

X rays of slices of the human torso at different angles

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7
Q

How do CT scanners have a high contrast?

A

Removes scattered rays and rays that aren’t absorbed

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8
Q

Why are CT’s less dangerous?

A

Only hit one place once

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9
Q

Why is an x ray machine covered in lead?

A

So they only go in one direction

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10
Q

How do CT scanners have a high resolution?

A

Smaller wavelength
Narrow beam
CCD not a film

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11
Q

What type of waves are ultrasound waves?

A

Longitudinal waves

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12
Q

What frequency are ultrasound waves?

A

Above hearing range

20-20000Hz

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13
Q

What wave length do ultrasound waves have?

A

1/10mm to 1mm in soft tissue

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14
Q

How does ultra sound work?

A

When waves pass through a different media they change speed
Some are reflected, transmitted or absorbed
They time how long it takes for the reflected rays the come back and create an image with them

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15
Q

How can ultra sound be used?

A

Look at babies

Break up kidney stones

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16
Q

What’s good about the resolution of ultra sound?

A

High without compromising strength of reflected signal

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17
Q

Which way to rays go from air to glass?

A

Towards the normal

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18
Q

How do lens form an image?

A

Refracting light

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19
Q

How do you find the refracted angles?

A

Sin I/ n x Sin r

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20
Q

The larger the refractive index, the _______ change in direction

A

Larger

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21
Q

Where do the rays go on a converging diagram?

A

Through the centre
Straight to the line then down to the F
Through the first F to the line then straight

22
Q

For a object behind the focal point what are the properties of the image?

A

Inverted
Virtual
Magnified

23
Q

What are the properties for an object in front of the focal point in a converging lens?

A

Magnified
Real
Upright

24
Q

Where are the rays on a diverging rays diagram?

A

Through the centre
Straight across then up from the left focal point
Down to the right focal point then straight from the centre line

25
Q

Properties of an image through a diverging lens?

A

Virtual
Diminished
Upright

26
Q

What is a real image?

A

Light rays meet

27
Q

How do you find magnification?

A

Height of image/ height of object

28
Q

What does a lens do?

A

Focus’ light into the retina

29
Q

What does the pupil do?

A

Takes light in so the eye can focus

30
Q

What does the cornea do?

A

Main refractive power

Converged light to an image

31
Q

What does the iris do?

A

Controls the amount of light entering the eye

32
Q

What does the ciliary muscle do?

A

Controls accommodation

33
Q

What does the suspensory ligament do?

A

Holds the lens in place

34
Q

What does the retina do?

A

Contains light receptors
Cones for colour
Rods for dim light and black and white

35
Q

What is adult vision?

A

25cm to infinity

36
Q

What’s accommodation?

A

How the eye focus’ of objects at different distances

37
Q

For an object that’s near what happens in the eye?

A

Ciliary muscle contracts
Suspensory ligament slacks
Muscle tension is low
Lens is fat

38
Q

For an object that far away what is the eye like?

A

Ciliary muscle relaxes
Suspensory ligament stretches
Muscle tension is high
Lens is thin

39
Q

How do you find the power of a lens?

A

Power = 1/ focal length

40
Q

How is focal length determined?

A

Refractive index

Curvature of material

41
Q

For a given focal length, the greater the refractive index, the _____ the lens?

A

Flatter

42
Q

If your short sighted whats wrong?

A

Too much refraction

Eye too long

43
Q

If your long sighted what’s wrong?

A

Eye too short

Not enough refraction

44
Q

For short sighted people what lens are in glasses?

A

Diverging

45
Q

For long sighted people what lens are in glasses?

A

Converging

46
Q

What’s accommodation on a camera?

A

Lens moving in and out

47
Q

What’s the retina in a camera?

A

Photographic film or CCD

48
Q

What’s total internal refraction?

A

Angle going in is greater than the critical angle

More to less dense

49
Q

How do you find the critical angle?

A

N=1/sin c

50
Q

What are the uses of total internal refraction?

A

Binoculars
Optical fibres
Endoscopy ( first bundle are incoherent but second bundle are in order to form an image)

51
Q

What 4 properties of laser are different to light?

A

Higher intensity
One frequency (monochromatic)
Beam is columated
Light emitted is coherent

52
Q

What precautions need to be taken with lasers?

A

In a lab
Dark safety goggles
Work below eye level
No reflective surfaces

53
Q

Uses of lasers?

A

Cutting things with no drag so it’s more precise
Heat sealing
Laser eye surgery to reshape the cornea

Physics (10 decks)

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