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P3 - Physics > Medical Applications Of Physics > Flashcards

Medical Applications Of Physics Flashcards

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1
Q

Why are X-Ray’s so dangerous?

A

They can damage the living tissue when they pass through it

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2
Q

What can we say about the absorption of X-Ray’s when they pass through the body?

A

X-rats are absorbed more by bones and teeth than by soft tissues

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3
Q

What is a CT scan?

A

CT scans distinguish between different types of soft tissue as well as between bone or teeth and soft tissue

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4
Q

What do we use X-Ray’s in hospitals for?

A

To make images and CT scans

To destroy tumours at or near the surface

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5
Q

What are ultrasound waves?

A

Sound waves of frequency above 20,000 Hz

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6
Q

What are ultrasound waves used for in medicine?

A

Ultrasound waves are used in medicine for ultrasound scanning and the destruction of kidney stones

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7
Q

Why can ultrasound waves be used to X scan the human body?

A

Ultra sound waves are partly reflected at a boundary between two different types of body tissue

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8
Q

Why is an ultrasound scan safer than taking an X-Ray photograph?

A

An ultrasound scan is non-ionising so it is safer than an X-Ray

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9
Q

How can we calculate the refractive index from the angles of incidence and refraction of a light Ray?

A

n= sin i / sin r

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10
Q

How is the critical angle related to the refractive index of the substance?

A

Refractive index =

1/sin*critical angle

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11
Q

What do doctors use an endoscope for?

A

An endoscope is used to see inside the body directly

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12
Q

What is a converging (convex) lens?

A

A converging (convex) lens focuses parallel Ray’s to a point called the principal focus

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13
Q

What is a diverging (concave) lens?

A

A diverging (concave)lens makes parallel Ray’s spread out as if they came from a point called the principal focus

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14
Q

what is the formula for magnification?

A

Image height divided by object height

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15
Q

What is the range of vision of a normal human eye?

A

The normal human eye had a range of vision from 25cm to infinity

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16
Q

What is the formula for power of a lens?

A

1/f

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17
Q

What is short sight and how is it corrected?

A

A short sighted eye is an eye that can only see near objects clearly - a diverging lens is used to correct it

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18
Q

What is long sight and how is it corrected?

A

A long sighted eye is an eye that can only see distant objects clearly - converging lens to correct it

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19
Q

Why is the refractive index of glass important in making spectacle lenses?

A

The higher the refractive index of the glass used to make a spectacle lens, the flatter and thinner the lens can be

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20
Q

How can we find the position and nature of an image formed by a lens?

A

A day diagram can be drawn to find the position and nature of an image formed by a lens

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21
Q

What type of lens is used in a camera and in a magnifying glass?

A

A camera contains a converging lens that is used to form a real image of an object

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22
Q

How does the height of the frequency effect the wave?

A

The higher the frequency the closer together the wave is

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23
Q

If the frequency is higher what does it mean for the quality of the image or sound?

A

The resolution is better

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24
Q

Why is an ultra sound safer than an X-ray?

A

It is non ionising whilst an X-ray is

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25
Q

How do you hear a sound?

A

Sound hits a surface and reflects off it

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26
Q

What is frequency?

A

Waves per second

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27
Q

What three things can happen to a Ray?

A

It can be
Totally internally reflected
Refracted
Critical angle

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28
Q

What happens when light travels inside a block?

A

It becomes slower

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29
Q

What is a critical angle?

A

When the Ray stops refracting and starts reflecting

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30
Q

Where are all Ray’s focuses?

A

At the focal point

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31
Q

What is the link between light and the shape of the lens?

A

The shape of a lens means that where the light hits it controls how it behaves

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32
Q

In a Ray diagram how can you tell if the image is real or fake?

A

If the lines cross over then the image is real if they don’t it is fake

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33
Q

How do you find the magnification from these diagrams?

A

1 measure object and image

2 use the equation real image divide by fake image

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34
Q

In a Ray diagram what does the length of the line mean for the image?

A

If it is larger the line is magnified

If it is smaller the line id smaller

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35
Q

In a Ray diagram what does the axis mean for the image?

A

Positive axis is the right way up

Negative axis is inverted

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36
Q

For a diverging lens the image would always be?

A

Diminished
Upright
Virtual
Always in front of the object

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37
Q

Is a diverging lens positive or negative?

A

Negative

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38
Q

Is a converging lens positive or negative?

A

Positive

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39
Q

What does refractive power mean?

A

The strength of the corrective lens

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40
Q

What problems do people with long sightedness have?

A

Only see distant objects clearly

Converging lens used to correct it

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41
Q

What problems do people with short sightedness have?

A

Only see near objects clearly

Diverging lens is used to correct it

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42
Q

What is the problem of ionisation?

A

They change DNA and cause cancer

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43
Q

What are X Ray’s part of?

A

The electromagnetic spectrum

44
Q

Property of X-rays?

A

Short wavelength which is about the length of an atom
Affect photographic film in the same way as light
Absorbers by metal and bone
Transmitted by soft tissue

45
Q

What do CT scans give you?

A

A 3D image using X-Ray’s taken from different positions or angles

46
Q

What can X-rays be used for medically?

A

Bone fractures
Dental problems
Killing cancer cells

47
Q

What can you do as a precaution against X Ray’s?

A

Wear lead aprons
Stand behind lead screens
Exposure kept to a minimum - radiographer a wear badges to monitor and regulate exposure

48
Q

What can electronic systems be used to produce?

A

Ultrasound waves

49
Q

What are properties of ultrasound waves?

A

Deflected at the boundary between 2 different media

The time taken for the reflections to reach the detector can be used to determine how far away the boundary is

50
Q

What equation can be used to find the distance travelled by an ultrasound wave?

A

S ( distance in m )

=

T (time in seconds) X V (speed in m/s)

51
Q

How can ultrasound waves be used in medicine?

A

For prenatal scanning

Removing kidney stones

52
Q

How can you know using a diagram of an image is real?

A

If the image is a different side to the object

53
Q

How can you know using a diagram of an image is virtual?

A

If it is on the same size as the object

54
Q

Using Ray diagrams how can they be described?

A

Upright
Inverted
Diminished
Magnified

55
Q

What is the pupils job?

A

Allows light to pass through as it enters eye

56
Q

What causes long sight?

A

Caused by a too short eyeball or inability to focus

57
Q

What causes short sight?

A

Too long an eyeball it inability into focus

58
Q

what is the ‘range of vision’

A

The near point for humans is 25cm

The far point for humans is infinity

59
Q

What can lasers also be used for?

A

An energy source for cutting
Burning
Cauterising

60
Q

How can lasers be used to help eyes?

A

To repair damaged retinas and correct vision defects

61
Q

How can lasers be used after surgery?

A

Lasers are used to destroy damaged tissue or stop bleeding - this is cauterising

62
Q

What are optical fibres?

A

Things that carry visible light over long distances

63
Q

When does total internal reflection occur?

A

When a wave travels through a dense substance towards a less dense substance

64
Q

What is the centre of mass?

A

The part of an object where the mass of an object is thought to be concentrated

65
Q

Where is the centre of mass in a symmetrical object?

A

Along the axis of symmetry

66
Q

If an object is freely suspended when will it reach its centre of mass?

A

When it is directly under the point of suspension

67
Q

When an object had a low centre of mass what does that mean?

A

It is less likely to topple than one with w high centre of mass

68
Q

What does the length of the pendulum mean?

A

The longer the pendulum the longer the time period

69
Q

Give examples of places where pendulums are used?

A

Simple fair ground rides and playground rides

70
Q

Why is endoscope ng positive?

A

Surgeons only have to cut small holes to operate

71
Q

Industrial use of ultrasound?

A

Cleaning something like a watch

Sonar

72
Q

What type of wave is an ultrasound wave?

A

Longitudinal

73
Q

What hearing range to most children have?

A

20 Hz to 20,000 Hz

74
Q

What word is used to describe a sound beyond the human hearing range?

A

Ultrasonic

75
Q

What is the cause of sound?

A

Vibrations in the air

76
Q

What does CT scan stand for?

A

Computerised tomography

77
Q

What is the wavelength of an x Ray equal to?

A

The diameter of an atom

78
Q

In Ray diagrams how are convex lenses represented?

A

Upward and downward arrows

79
Q

In concave lens diagram how is it represented?

A

Inverted upward and downward arrows

80
Q

How can X-Rays be used?

A
  • bone fractures
  • CT scans
  • killing cancer cells
  • dental problems
81
Q

How are images formed electronically from X-Ray’s?

A

Charge-coupled devices

CCDs

82
Q

How are ultrasound waves produced?

A

By electronic systems

83
Q

How can you determine how far away a boundary is?

A

Time taken for the reflections to reach a detector

84
Q

What is velocity measured in?

A

M/s

85
Q

How can ultrasound waves be used?

A
  • pre natal scanning

* removal of kidney stones

86
Q

How does a lens form an image?

A

Refracting light

87
Q

Definition of refraction?

A

Change of direction of light as it passes from one medium to another

88
Q

How is a converging lens used?

A

As a magnifying glass

To treat long sight

89
Q

What do the ciliary muscles do?

A

Change the shape of the lens

Which allows light to be focuses at varying distances

90
Q

What is the range of vision?

A

The eye can focus an object between a near point and a far point

91
Q

How can you produce ultrasound?

A

By electronic systems

92
Q

On a diagram how can you tell if an image is real?

A

If it is on a different side of the object

93
Q

On a diagram how can you tell if an image is virtual?

A

If it is on the same size of the object

94
Q

How to find the centre of mass in experiment?

A

Make small hole in object
Suspend it from this point so it can swing freely
Hang plumb line from same point and allow it to stop moving
Mark vertically shown by plumb line
Make another hole and repeat
Repeat again
The centre or mere is the point at which all lines cross

95
Q

Examples of simple levers?

A

Wheelbarrows
Scissors
Long sticks or bars

96
Q

What does a CT scan produce?

A

A 3D digital image of any cross section of the body

97
Q

How does a CT scan work?

A

X ray tube automatically moves round the inside ring in small steps
Each position X Ray’s from the tube pass through the patient and reach the detector ring
Electronic signals from the detector are recorded by a computer until the tube has moved around the ring
Computer displays a digital image of scanned areas

98
Q

What does the detector signal depend on?

A

Different types of tissue along the X Ray path

How far the X Ray pass through each type of tissue

99
Q

When will total internal reflection occur?

A

When the angle of reflection is equal to the angle of incidence

100
Q

What does the position and nature of the image depend on?

A

Focal length

The distance from the object to the lens

101
Q

Describe an X Ray?

A 
Electromagnetic waves
High frequency
High energy
Short wavelength 
Similar diameter to ah atom
Transverse wave
Ionising radiation
102
Q

Describe ultrasound?

A

Frequency of above 20000 Hz
Beyond human hearing
Longitudinal wave

103
Q

What happens when an X Ray is inside the body?

A

Absorbed by bone

Transmitted by tissue

104
Q

What happens when ultrasound is inside the body?

A

Partially reflect at the boundary of two media

Travels at different speeds through different media

105
Q

Where is the alternating magnetic field produced?

A

In the core

106
Q

Advantages of switch mode transformers?

A

Smaller
Lighter
Little energy needed
More efficient

P3 - Physics (4 decks)

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