P3 Chapter 1 Medical Applications in Physics Part 2

Topics covered:

-Correcting vision
-Total internal reflection
-Lasers

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What is the near and far point of a normal eye?
Near: 25cm Far: Infinity
1 of 25
What can people with long-sight (hyperopia) not focus on?
Nearby objects
2 of 25
What are the reasons for long sight?
Eyeball=too short and lens becomes too elastic=>not thick enough
3 of 25
Therefore where is the light focused?
Behind the retina
4 of 25
How do we treat long-sight with what power?
Use a converging lens which has positive power
5 of 25
What can people with short-sight (myopia) not focus on?
Distant objects
6 of 25
Therefore what is the far point?
Far point is less that infinity
7 of 25
What are the reasons for short sight?
Eyeball=too long and lens is too thick
8 of 25
Therefore where is the light focused?
On a point in front of the retina.
9 of 25
How do we treat short sight and what is the power?
By using a diverging lens (partial unfocus) and negative power
10 of 25
What happens to light when it is refracted with [i] being less than the critical angle?
Light changes direction and changes speed as it passes out.
11 of 25
How much is internally reflected?
Little as most light passes out
12 of 25
What happens to the light when [i] is equal to the critical angle?
Light skims surface of the glass.
13 of 25
How much is internally reflected?
Quite a bit.
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What happens to light when [i] is more than the critical angle?
The ray is totally internally reflected. (Total internal reflection)
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What is the angle of reflection equal to?
Angle of refraction
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What does the value of the critical angle depend on?
The refractive index.
17 of 25
What size critical angle do dense materials with high reflective index?
A low critical angle
18 of 25
What is the formula for finding the critical angle/refracted index?
Refracted index, n=1/sin of critical angle, C
19 of 25
What are some uses of total internal reflection?
Optical fibres-endoscope, broadband
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What are optical fibres good for?
Carrying light over LONG distances quickly
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What are the two bundles of optical fibres used for in the endoscope?
light and the image
22 of 25
How do we see the image?
Through an eyepiece or on a TV screen
23 of 25
What are lasers?
A narrow intense beam of light
24 of 25
What are lasers used for?
Laser cutting, cauterisation, skin conditions, laser eye surgery
25 of 25

Other cards in this set

Card 2

Front

What can people with long-sight (hyperopia) not focus on?

Back

Nearby objects

Card 3

Front

What are the reasons for long sight?

Back

Preview of the front of card 3

Card 4

Front

Therefore where is the light focused?

Back

Preview of the front of card 4

Card 5

Front

How do we treat long-sight with what power?

Back

Preview of the front of card 5
View more cards

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