P3.1 Medicle Physics

Question 0

Proportions of x rays?

Answer 0

Short wavelength

Very ionising

Question 1

What length are x-rays?

Answer 1

10^-10m

Question 2

How does an x ray work?

Answer 2

It’s absorbed by more dense materials like bone and metal but is transmitted through soft tissue creating an imagine

Question 3

Uses of x rays?

Answer 3

Diagnosis
Treatment
Plan treatment

Question 4

How are x rays made?

Answer 4

An accelerating electron hits atoms in a heavy metal target which emits them

Question 5

What precautions need to be taken with x rays?

Answer 5

DES

Question 6

What are CT scans?

Answer 6

X rays of slices of the human torso at different angles

Question 7

How do CT scanners have a high contrast?

Answer 7

Removes scattered rays and rays that aren’t absorbed

Question 8

Why are CT’s less dangerous?

Answer 8

Only hit one place once

Question 9

Why is an x ray machine covered in lead?

Answer 9

So they only go in one direction

Question 10

How do CT scanners have a high resolution?

Answer 10

Smaller wavelength
Narrow beam
CCD not a film

Question 11

What type of waves are ultrasound waves?

Answer 11

Longitudinal waves

Question 12

What frequency are ultrasound waves?

Answer 12

Above hearing range

20-20000Hz

Question 13

What wave length do ultrasound waves have?

Answer 13

1/10mm to 1mm in soft tissue

Question 14

How does ultra sound work?

Answer 14

When waves pass through a different media they change speed
Some are reflected, transmitted or absorbed
They time how long it takes for the reflected rays the come back and create an image with them

Question 15

How can ultra sound be used?

Answer 15

Look at babies

Break up kidney stones

Question 16

What’s good about the resolution of ultra sound?

Answer 16

High without compromising strength of reflected signal

Question 17

Which way to rays go from air to glass?

Answer 17

Towards the normal

Question 18

How do lens form an image?

Answer 18

Refracting light

Question 19

How do you find the refracted angles?

Answer 19

Sin I/ n x Sin r

Question 20

The larger the refractive index, the _______ change in direction

Answer 20

Larger

Question 21

Where do the rays go on a converging diagram?

Answer 21

Through the centre
Straight to the line then down to the F
Through the first F to the line then straight

Question 22

For a object behind the focal point what are the properties of the image?

Answer 22

Inverted
Virtual
Magnified

Question 23

What are the properties for an object in front of the focal point in a converging lens?

Answer 23

Magnified
Real
Upright

Question 24

Where are the rays on a diverging rays diagram?

Answer 24

Through the centre Straight across then up from the left focal point Down to the right focal point then straight from the centre line

Question 25

Properties of an image through a diverging lens?

Answer 25

Virtual Diminished Upright

Question 26

What is a real image?

Answer 26

Light rays meet

Question 27

How do you find magnification?

Answer 27

Height of image/ height of object

Question 28

What does a lens do?

Answer 28

Focus' light into the retina

Question 29

What does the pupil do?

Answer 29

Takes light in so the eye can focus

Question 30

What does the cornea do?

Answer 30

Main refractive power | Converged light to an image

Question 31

What does the iris do?

Answer 31

Controls the amount of light entering the eye

Question 32

What does the ciliary muscle do?

Answer 32

Controls accommodation

Question 33

What does the suspensory ligament do?

Answer 33

Holds the lens in place

Question 34

What does the retina do?

Answer 34

Contains light receptors Cones for colour Rods for dim light and black and white

Question 35

What is adult vision?

Answer 35

25cm to infinity

Question 36

What's accommodation?

Answer 36

How the eye focus' of objects at different distances

Question 37

For an object that's near what happens in the eye?

Answer 37

Ciliary muscle contracts Suspensory ligament slacks Muscle tension is low Lens is fat

Question 38

For an object that far away what is the eye like?

Answer 38

Ciliary muscle relaxes Suspensory ligament stretches Muscle tension is high Lens is thin

Question 39

How do you find the power of a lens?

Answer 39

Power = 1/ focal length

Question 40

How is focal length determined?

Answer 40

Refractive index | Curvature of material

Question 41

For a given focal length, the greater the refractive index, the _____ the lens?

Answer 41

Flatter

Question 42

If your short sighted whats wrong?

Answer 42

Too much refraction | Eye too long

Question 43

If your long sighted what's wrong?

Answer 43

Eye too short | Not enough refraction

Question 44

For short sighted people what lens are in glasses?

Answer 44

Diverging

Question 45

For long sighted people what lens are in glasses?

Answer 45

Converging

Question 46

What's accommodation on a camera?

Answer 46

Lens moving in and out

Question 47

What's the retina in a camera?

Answer 47

Photographic film or CCD

Question 48

What's total internal refraction?

Answer 48

Angle going in is greater than the critical angle | More to less dense

Question 49

How do you find the critical angle?

Answer 49

N=1/sin c

Question 50

What are the uses of total internal refraction?

Answer 50

Binoculars Optical fibres Endoscopy ( first bundle are incoherent but second bundle are in order to form an image)

Question 51

What 4 properties of laser are different to light?

Answer 51

Higher intensity One frequency (monochromatic) Beam is columated Light emitted is coherent

Question 52

What precautions need to be taken with lasers?

Answer 52

In a lab Dark safety goggles Work below eye level No reflective surfaces

Question 53

Uses of lasers?

Answer 53

Cutting things with no drag so it's more precise Heat sealing Laser eye surgery to reshape the cornea