P3 Chapter 1 Medical Applications in Physics Part 1

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What spectrum are X-rays part of?
Electromagnetic spectrum
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What type of wave are x-rays?
Transverse waves
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What are the FEATURES of x-rays?
Short wavelength, high frequency, high energy
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Why can x-rays increase the risk of cancer?
High energy causes ionisation which causes mutations
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How do x-rays affect photographic film?
In the same way as light
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What are x-rays absorbed by?
Bone, metal, teeth etc
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What are x-rays transmitted by?
Soft tissue eg/muscle
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What is the rough wavelength of x-rays?
The diameter of an atom
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What are x-rays good at seeing in the body?
Bone fractures, dental problems
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What is the quality of a CT scanned image?
High resolution, 3D images of the whole body
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How are electronic images produced using a CT scanner?
They use charge-coupled devices (CCPs)
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Why must we limit our exposure to x-rays? eg/ in hospitals
They are ionising which increases the risk of cancer
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How can we take precautions when using x-rays?
Wear a lead apron, stand behind a lead screen, leave the room
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What is the frequency range of human hearing?
20Hz-20,000Hz
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Therefore, what is ultrasound?
Frequency higher than upper limit of human hearing >20000Hz
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What does ultrasound partially reflect off?
The boundary between TWO DIFFERENT DENSITIES
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Give examples of what ultrasound could possibly detect.
Kidneys (stones), heart, foetus
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How do you determine the distance using ultrasound? (equation)
Distance,S(m)=Speed,V(m/s) x Time,t(s)
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If you are asked to find the depth of the sea, what is the one key thing to remember?
You must halve the distance the pulse travelled
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What are some medical uses of ultrasound?
Imaging(foetus), doppler scanning-blood, kidney stones
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What happens to light when it enters a different medium?
It changes direction and changes speed.
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When light slows down, what happens to the direction it travels in?
It bends towards the normal
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When light speeds back up, what happens to the direction it travels in?
It bends away from the normal
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What happens if a ray of light travels along the normal in glass?
It will not change direction, but certainly slow down.
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What are the two types of lenses?
Converging (convex) and Diverging (Concave)
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What does a converging lens do to parallel rays of light?
Converges (moves together) the rays of light to a point (focus)
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What is the principal focus in a converging lens?
The point where all the rays meet.
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What is the principal axis?
The line that passes through the middle of a lens.
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What is the principal focus in a diverging lens?
The point where the rays hitting the lens appears to come from
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What is the focal length?
The distance from the lens to the principal focus.
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How do we calculate refractive index? (equation)
n= sin i/sin r
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What is the symbol arrow for converging lenses?
Arrow heads point away from each other
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Draw a converging lens ray diagram.
1.Line parallel to axis 2.Line through F 3.Line though the centre
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What is the symbol arrow for a diverging lens?
Arrows pointing towards each other
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Draw a diverging lens ray diagram.
1. Line parallel(axis)2.Line from image F 3.Line through centre
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What will the image of a diverging lens always be?
VIRTUAL.
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In a converging lens, what is the nature of the image between 2F and F?
Inverted, larger than object and real
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At object 2F, what will the nature of the image be?
Real, inverted and exactly the same size as object
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An object nearer than 2F?
Virtual, upright and same side as lens
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Of a diverging lens, what will the nature of the image be?
Smaller, upright and VIRTUAL ALWAYS
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Draw a ray diagram of a converging lens less than F
1. Parallel to axis then through F. 2. Centre 3. Dotted line back.
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What will the nature of the image for a magnifying glass be?
Larger, Upright and Virtual
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What is a real image?
An image where rays converge and form an image on a screen
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What is a virtual image?
Diverging rays and rays appear to come from a different place
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How do we find out how powerful a lens is?
Power, P(D)=1/Focal length, f(m)
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If we decrease the focal length, what should happen to the power?
It should increase.
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What are the two factors that determine power?
The curvature of the 2 lens surfaces, refractive index of material
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How do we make them more powerful lenses?
Make them strongly curved and have high refractive index
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What are the parts of the eye?
cornea,iris,pupil,lens,ciliary muscles,suspensory ligaments,retina
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What does the cornea do?
Transparent and focuses light by a fixed amount
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What does the iris and pupil do?
Controls amount of light. Protects eye from too much light
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What does the lens do?
Focuses light and changes shape for near/distant focusing
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What do ciliary muscles and suspensory ligaments do?
They work together to change the shape of the lens.
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What does the retina do?
Detects light and sends impulses to the brain.
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What two things in a camera are equivalent to the retina?
Camera film and charge-coupled devices (CCDs)
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Distant Objects (DO): how much does the eye need to be focused?
Only a small amount
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DO: What happens to the ciliary muscles?
They relax
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DO: Therefore, what happens to the suspensory ligaments?
They taut.
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DO: What happens to the lens to there cause less focusing?
Lens becomes stretched and narrow.
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Near Objects (NO): How much does the eye need to be focused?
A larger amount
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NO: What happens to the ciliary muscles?
They contract
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NO: Therefore, what happens to the suspensory ligaments?
They slacken
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NO: What happens to the lens to there cause more powerful?
Lens flattens
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Other cards in this set

Card 2

Front

What type of wave are x-rays?

Back

Transverse waves

Card 3

Front

What are the FEATURES of x-rays?

Back

Preview of the front of card 3

Card 4

Front

Why can x-rays increase the risk of cancer?

Back

Preview of the front of card 4

Card 5

Front

How do x-rays affect photographic film?

Back

Preview of the front of card 5
View more cards

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