# P3 Chapter 1 Medical Applications in Physics Part 1

HideShow resource information
What spectrum are X-rays part of?
Electromagnetic spectrum
1 of 63
What type of wave are x-rays?
Transverse waves
2 of 63
What are the FEATURES of x-rays?
Short wavelength, high frequency, high energy
3 of 63
Why can x-rays increase the risk of cancer?
High energy causes ionisation which causes mutations
4 of 63
How do x-rays affect photographic film?
In the same way as light
5 of 63
What are x-rays absorbed by?
Bone, metal, teeth etc
6 of 63
What are x-rays transmitted by?
Soft tissue eg/muscle
7 of 63
What is the rough wavelength of x-rays?
The diameter of an atom
8 of 63
What are x-rays good at seeing in the body?
Bone fractures, dental problems
9 of 63
What is the quality of a CT scanned image?
High resolution, 3D images of the whole body
10 of 63
How are electronic images produced using a CT scanner?
They use charge-coupled devices (CCPs)
11 of 63
Why must we limit our exposure to x-rays? eg/ in hospitals
They are ionising which increases the risk of cancer
12 of 63
How can we take precautions when using x-rays?
Wear a lead apron, stand behind a lead screen, leave the room
13 of 63
What is the frequency range of human hearing?
20Hz-20,000Hz
14 of 63
Therefore, what is ultrasound?
Frequency higher than upper limit of human hearing >20000Hz
15 of 63
What does ultrasound partially reflect off?
The boundary between TWO DIFFERENT DENSITIES
16 of 63
Give examples of what ultrasound could possibly detect.
Kidneys (stones), heart, foetus
17 of 63
How do you determine the distance using ultrasound? (equation)
Distance,S(m)=Speed,V(m/s) x Time,t(s)
18 of 63
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
19 of 63
What are some medical uses of ultrasound?
Imaging(foetus), doppler scanning-blood, kidney stones
20 of 63
What happens to light when it enters a different medium?
It changes direction and changes speed.
21 of 63
When light slows down, what happens to the direction it travels in?
It bends towards the normal
22 of 63
When light speeds back up, what happens to the direction it travels in?
It bends away from the normal
23 of 63
What happens if a ray of light travels along the normal in glass?
It will not change direction, but certainly slow down.
24 of 63
What are the two types of lenses?
Converging (convex) and Diverging (Concave)
25 of 63
What does a converging lens do to parallel rays of light?
Converges (moves together) the rays of light to a point (focus)
26 of 63
What is the principal focus in a converging lens?
The point where all the rays meet.
27 of 63
What is the principal axis?
The line that passes through the middle of a lens.
28 of 63
What is the principal focus in a diverging lens?
The point where the rays hitting the lens appears to come from
29 of 63
What is the focal length?
The distance from the lens to the principal focus.
30 of 63
How do we calculate refractive index? (equation)
n= sin i/sin r
31 of 63
What is the symbol arrow for converging lenses?
Arrow heads point away from each other
32 of 63
Draw a converging lens ray diagram.
1.Line parallel to axis 2.Line through F 3.Line though the centre
33 of 63
What is the symbol arrow for a diverging lens?
Arrows pointing towards each other
34 of 63
Draw a diverging lens ray diagram.
1. Line parallel(axis)2.Line from image F 3.Line through centre
35 of 63
What will the image of a diverging lens always be?
VIRTUAL.
36 of 63
In a converging lens, what is the nature of the image between 2F and F?
Inverted, larger than object and real
37 of 63
At object 2F, what will the nature of the image be?
Real, inverted and exactly the same size as object
38 of 63
An object nearer than 2F?
Virtual, upright and same side as lens
39 of 63
Of a diverging lens, what will the nature of the image be?
Smaller, upright and VIRTUAL ALWAYS
40 of 63
Draw a ray diagram of a converging lens less than F
1. Parallel to axis then through F. 2. Centre 3. Dotted line back.
41 of 63
What will the nature of the image for a magnifying glass be?
Larger, Upright and Virtual
42 of 63
What is a real image?
An image where rays converge and form an image on a screen
43 of 63
What is a virtual image?
Diverging rays and rays appear to come from a different place
44 of 63
How do we find out how powerful a lens is?
Power, P(D)=1/Focal length, f(m)
45 of 63
If we decrease the focal length, what should happen to the power?
It should increase.
46 of 63
What are the two factors that determine power?
The curvature of the 2 lens surfaces, refractive index of material
47 of 63
How do we make them more powerful lenses?
Make them strongly curved and have high refractive index
48 of 63
What are the parts of the eye?
cornea,iris,pupil,lens,ciliary muscles,suspensory ligaments,retina
49 of 63
What does the cornea do?
Transparent and focuses light by a fixed amount
50 of 63
What does the iris and pupil do?
Controls amount of light. Protects eye from too much light
51 of 63
What does the lens do?
Focuses light and changes shape for near/distant focusing
52 of 63
What do ciliary muscles and suspensory ligaments do?
They work together to change the shape of the lens.
53 of 63
What does the retina do?
Detects light and sends impulses to the brain.
54 of 63
What two things in a camera are equivalent to the retina?
Camera film and charge-coupled devices (CCDs)
55 of 63
Distant Objects (DO): how much does the eye need to be focused?
Only a small amount
56 of 63
DO: What happens to the ciliary muscles?
They relax
57 of 63
DO: Therefore, what happens to the suspensory ligaments?
They taut.
58 of 63
DO: What happens to the lens to there cause less focusing?
Lens becomes stretched and narrow.
59 of 63
Near Objects (NO): How much does the eye need to be focused?
A larger amount
60 of 63
NO: What happens to the ciliary muscles?
They contract
61 of 63
NO: Therefore, what happens to the suspensory ligaments?
They slacken
62 of 63
NO: What happens to the lens to there cause more powerful?
Lens flattens
63 of 63

## Other cards in this set

### Card 2

#### Front

What type of wave are x-rays?

Transverse waves

### Card 3

#### Front

What are the FEATURES of x-rays?

### Card 4

#### Front

Why can x-rays increase the risk of cancer?

### Card 5

#### Front

How do x-rays affect photographic film?