# Radiation in Treatment and Medicine

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• Created by: beth213
• Created on: 28-01-14 17:24
What is intensity equal to?
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What is area equal to in this equation?
4πr^2
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How is radiation used for diagnosis in medincine?
CAT scans/X ray machines/ultrasound/ionising or non-ionising radiation
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How is radiation used for therapy?
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What is the law of incidence?
Angle of inciddence=angle of reflection
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What is the normal?
the angle at the right angle to the reflecting surface
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What is refraction?
a light ray that changes direction when it reaches a new medium
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When does light travel towards the normal?
when its moving in a material where it travels more slowly
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What is the critical angle?
the point at which the refracted light passes along the boundary
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What is total internal reflection?
when the angle of incidence is larger than the critical angle so the light is reflected back to the medium
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What is the refractive index?
the extent to which light is refacted when it enters a medium
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What is the angle of refraction at the critical angle?
90 degrees
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What are the refactive index's for air water and glass?
air=1, water=1.3, glass=1.5
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What does wave speed depend on?
the density of the material it's travelling through
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What's an endoscope used for?
to see inside the body
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How does an optical fibre work?
a light ray enters a long section of glass at an angle which gives total internal reflection the entire length of the glass.
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How does the whole endoscope work?
two bundles are used; one carries the beam to the object, the other returns the image to an eyepiece. the bundles are surrounded by a sodt coating so they don't harm the body
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Why are endoscopes useful in medicine?
they are non-invasive and are safe to use in pregnancy
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What is focal length?
the distance between the middle of the lens and the focus
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How is a converging lens made to refract light?
it is thicker in the middle than the ends so the lens can refract light to a focus.
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How is a diverging lens made to refract light?
it is thinner in the middle than the ends so it spreads light out
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What is the difference between a real and virtual image?
A real image can be projected onto a screen whereas a virtual image can't
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What is the lens formula?
1/f=1/u+1/v
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What do f, u, and v stand for?
f=focal length, u=object distance, v=image distance
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How do you know if the image is virtual or real?
if you get a negative number from the lens equation it is virtual
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What are the near and far points of the eye?
far is infinite for a normal eye, 25cm for near
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How do we see?
light comes through the cornea and is refracted. the iris controls how much light comes through the pupil and falls on the lens, the shape of which is changed by ciliary muscles. the light is refracted onto the retina to light sensitive receptors
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Why does short sightedness occur and how can it be fixed?
the light focuses before the retina so the image formed on the retina isn't clear. it can be fixed with diverging lenses
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Why does long sightedness occur and how can it be fixed?
the light seems to focus behinf the retina, so the image isn't clear. it can be fixed with converging lenses
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How does laser eye surgery work?
for short sight the focusing power is reduced by removing some of the thickness from the central cornea. long sight involves removing tissue at the edge increasing focusing power
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How does ultrasound work?
sound waves are transmitted to the body, and at boundaries between tissues and organs some waves are bounced back. the time taken for the echoes to return measures the depth of each layer.
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How is ultrasound used in medicine?
pregnancies, kidney stones, treating injuries
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## Other cards in this set

### Card 2

#### Front

What is area equal to in this equation?

4πr^2

### Card 3

#### Front

How is radiation used for diagnosis in medincine?

### Card 4

#### Front

How is radiation used for therapy?

### Card 5

#### Front

What is the law of incidence?