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P3 - Physics > Medical Applications Of Physics > Flashcards

Medical Applications Of Physics Flashcards

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
How do you hear a sound?
Sound hits a surface and reflects off it
26
What is frequency?
Waves per second
27
What three things can happen to a Ray?
It can be Totally internally reflected Refracted Critical angle
28
What happens when light travels inside a block?
It becomes slower
29
What is a critical angle?
When the Ray stops refracting and starts reflecting
30
Where are all Ray's focuses?
At the focal point
31
What is the link between light and the shape of the lens?
The shape of a lens means that where the light hits it controls how it behaves
32
In a Ray diagram how can you tell if the image is real or fake?
If the lines cross over then the image is real if they don't it is fake
33
How do you find the magnification from these diagrams?
1 measure object and image | 2 use the equation real image divide by fake image
34
In a Ray diagram what does the length of the line mean for the image?
If it is larger the line is magnified | If it is smaller the line id smaller
35
In a Ray diagram what does the axis mean for the image?
Positive axis is the right way up | Negative axis is inverted
36
For a diverging lens the image would always be?
Diminished Upright Virtual Always in front of the object
37
Is a diverging lens positive or negative?
Negative
38
Is a converging lens positive or negative?
Positive
39
What does refractive power mean?
The strength of the corrective lens
40
What problems do people with long sightedness have?
Only see distant objects clearly | Converging lens used to correct it
41
What problems do people with short sightedness have?
Only see near objects clearly | Diverging lens is used to correct it
42
What is the problem of ionisation?
They change DNA and cause cancer
43
What are X Ray's part of?
The electromagnetic spectrum
44
Property of X-rays?
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
What do CT scans give you?
A 3D image using X-Ray's taken from different positions or angles
46
What can X-rays be used for medically?
Bone fractures Dental problems Killing cancer cells
47
What can you do as a precaution against X Ray's?
Wear lead aprons Stand behind lead screens Exposure kept to a minimum - radiographer a wear badges to monitor and regulate exposure
48
What can electronic systems be used to produce?
Ultrasound waves
49
What are properties of ultrasound waves?
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
What equation can be used to find the distance travelled by an ultrasound wave?
S ( distance in m ) = T (time in seconds) X V (speed in m/s)
51
How can ultrasound waves be used in medicine?
For prenatal scanning | Removing kidney stones
52
How can you know using a diagram of an image is real?
If the image is a different side to the object
53
How can you know using a diagram of an image is virtual?
If it is on the same size as the object
54
Using Ray diagrams how can they be described?
Upright Inverted Diminished Magnified
55
What is the pupils job?
Allows light to pass through as it enters eye
56
What causes long sight?
Caused by a too short eyeball or inability to focus
57
What causes short sight?
Too long an eyeball it inability into focus
58
what is the 'range of vision'
The near point for humans is 25cm The far point for humans is infinity
59
What can lasers also be used for?
An energy source for cutting Burning Cauterising
60
How can lasers be used to help eyes?
To repair damaged retinas and correct vision defects
61
How can lasers be used after surgery?
Lasers are used to destroy damaged tissue or stop bleeding - this is cauterising
62
What are optical fibres?
Things that carry visible light over long distances
63
When does total internal reflection occur?
When a wave travels through a dense substance towards a less dense substance
64
What is the centre of mass?
The part of an object where the mass of an object is thought to be concentrated
65
Where is the centre of mass in a symmetrical object?
Along the axis of symmetry
66
If an object is freely suspended when will it reach its centre of mass?
When it is directly under the point of suspension
67
When an object had a low centre of mass what does that mean?
It is less likely to topple than one with w high centre of mass
68
What does the length of the pendulum mean?
The longer the pendulum the longer the time period
69
Give examples of places where pendulums are used?
Simple fair ground rides and playground rides
70
Why is endoscope ng positive?
Surgeons only have to cut small holes to operate
71
Industrial use of ultrasound?
Cleaning something like a watch | Sonar
72
What type of wave is an ultrasound wave?
Longitudinal
73
What hearing range to most children have?
20 Hz to 20,000 Hz
74
What word is used to describe a sound beyond the human hearing range?
Ultrasonic
75
What is the cause of sound?
Vibrations in the air
76
What does CT scan stand for?
Computerised tomography
77
What is the wavelength of an x Ray equal to?
The diameter of an atom
78
In Ray diagrams how are convex lenses represented?
Upward and downward arrows
79
In concave lens diagram how is it represented?
Inverted upward and downward arrows
80
How can X-Rays be used?
* bone fractures * CT scans * killing cancer cells * dental problems
81
How are images formed electronically from X-Ray's?
Charge-coupled devices | CCDs
82
How are ultrasound waves produced?
By electronic systems
83
How can you determine how far away a boundary is?
Time taken for the reflections to reach a detector
84
What is velocity measured in?
M/s
85
How can ultrasound waves be used?
* pre natal scanning | * removal of kidney stones
86
How does a lens form an image?
Refracting light
87
Definition of refraction?
Change of direction of light as it passes from one medium to another
88
How is a converging lens used?
As a magnifying glass | To treat long sight
89
What do the ciliary muscles do?
Change the shape of the lens | Which allows light to be focuses at varying distances
90
What is the range of vision?
The eye can focus an object between a near point and a far point
91
How can you produce ultrasound?
By electronic systems
92
On a diagram how can you tell if an image is real?
If it is on a different side of the object
93
On a diagram how can you tell if an image is virtual?
If it is on the same size of the object
94
How to find the centre of mass in experiment?
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
Examples of simple levers?
Wheelbarrows Scissors Long sticks or bars
96
What does a CT scan produce?
A 3D digital image of any cross section of the body
97
How does a CT scan work?
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
What does the detector signal depend on?
Different types of tissue along the X Ray path | How far the X Ray pass through each type of tissue
99
When will total internal reflection occur?
When the angle of reflection is equal to the angle of incidence
100
What does the position and nature of the image depend on?
Focal length | The distance from the object to the lens
101
Describe an X Ray?
``` Electromagnetic waves High frequency High energy Short wavelength Similar diameter to ah atom Transverse wave Ionising radiation ```
102
Describe ultrasound?
Frequency of above 20000 Hz Beyond human hearing Longitudinal wave
103
What happens when an X Ray is inside the body?
Absorbed by bone | Transmitted by tissue
104
What happens when ultrasound is inside the body?
Partially reflect at the boundary of two media | Travels at different speeds through different media
105
Where is the alternating magnetic field produced?
In the core
106
Advantages of switch mode transformers?
Smaller Lighter Little energy needed More efficient

P3 - Physics (4 decks)

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