Unit 3

Question 1

X-Rays are transmitted through healthy tissue, what are they absorbed by?

Answer 1

Denser materials like bones and metal

Question 2

What can X-Rays be used for?

Answer 2

To see:
Bone fractures
Dental problems

Question 3

How are X-Rays formed?

Answer 3

Electronically using charge-coupled devices (CCDs)

Question 4

What are CCDs?

Answer 4

Silicon chip about the same size as a postage stamp, in which are divided up into a grid of identical pixels

Question 5

What do CCDs produce?

Answer 5

They produce electronic signals which are used to form high resolution images

Question 6

Define ‘CT’ scan

Answer 6

Computerised axial tomography

Question 7

What does a CT scan do?

Answer 7

Creates a 3D image of the inside of the body

Question 8

What does hight doses of X-Rays do?

Answer 8

Kill living cells

Question 9

What X Ray is used to treat cancer?

Answer 9

Gamma radiation

Question 10

How does the X-ray kill the cancer cell without the living cells being killed too?

Answer 10

The X-Rays have to be carefully focused at the right dosage to kill the cancer cells without damaging too many normal cells

Question 11

How do they treat cancer?

Answer 11

1) the X-rays are focused on the tumour using a wide beam.
2) the beam is rotated round the patient with the tumour at the centre.
3) this minimised the exposer of the normal cells and changes of damaging the rest of the body.

Question 12

What do radiographers have to wear for protection when doing a scan?

Answer 12

Wear a lead apron

Stand behind a lead screen or leave the room

Question 13

What size is an X-Ray wavelength?

Answer 13

Roughly the same size as the diameter of an atom

Question 14

What is done to protect the patient from the radiation?

Answer 14

A lead shield is put in place to protect the areas that aren’t being scanned

Question 15

What is the range of a humans hearing?

Answer 15

20 Hz to 20 000 Hz

Question 16

What is ultra sound?

Answer 16

Electrical oscillations of any frequency which is easily converted into mechanical vibrations to produce sound waves of a higher frequency than the upper limit of human hearing

Question 17

Where do ultrasound waves get partially reflected?

Answer 17

At a boundary between media

Question 18

How is ultrasound used in medicine?

Answer 18

Investigation blood flow
Heart problems
Check on fatal development

Question 19

What causes refraction?

Answer 19

The waves change direction and speed

Question 20

What are the 2 types of lens?

Answer 20

Converging

Diverging

Question 21

What’s a converging lens?

Answer 21

A converging lens is convex (it bulges outwards) it causes parallel Rays of light to converge (move together)

Question 22

What’s a diverging lens?

Answer 22

It’s concave (it caves inwards) it causes parallel Rays of light to diverge (spread out)

Question 23

What’s the ‘axis’ of a lens?

Answer 23

The line passing through the middle

Question 24

What’s the principal focus of a converging lens?

Answer 24

Where the light rays hitting the lens parallel to he axis all meet

Question 25

What’s the principal focus of a diverging lens?

Answer 25

Where the rays hitting the lens parallel to the axis appear to come from - you can trace them back until they all appear to meet up behind the lens

Question 26

What’s the principal focus of each side of the lens?

Answer 26

The distance from the centre of the lens to the principal focus is called the focal length

Question 27

How is a ‘real image’ constructed?

Answer 27

Where the light from the object comes together to form an image on a ‘screen’ - like the image formed on an eyes retina

Question 28

3 rules for refraction in a converging lens?

Answer 28

1) an incident Ray parallel to the axis refracts through the lens and passes through the principal focus on the other side
2) an incident Ray passes through the principal focus refracts through the lens and travels parallel to the axis
3) an incident Ray passing through the centre of the lens carries on in the same direction

Question 29

The 3 rules for refraction in a diverging lens?

Answer 29

1) the incident Ray parallel to the axis refracts through the lens and travels in line with the principal focus
2) an incident Ray passing through the lens towards the principal focus refracts through the lens and travels parallel to the axis
3) an incident Ray passing through he centre of the lens carries on in the same direction

Question 30

What uses a converging lens?

Answer 30

A magnifying glass

Question 31

THE EYE

What is a cornea?

Answer 31

A transparent ‘window’ with a convex shape, and a high refractive index

Question 32

THE EYE

What is the colourful part of the eye called and what is it controlled by?

Answer 32

The politic part is called the iris

It is made up of muscles that control the size of the pupil

Question 33

What is a pupil?

Answer 33

A hole in the middle of the iris

Question 34

What does the pupil do?

Answer 34

It controls the light intensity entering the eye

Question 35

THE EYE

Why does the lens change shape?

Answer 35

To focus light from objects at varying distances

Question 36

Where are images formed?

Answer 36

On the retina, which is covered in light sensitive cells

Question 37

Whats the furthest distance the eye can focus on comfortably?

Answer 37

Infinity

Question 38

What’s the shortest distance the eye can focus on comfortably?

Answer 38

Approx 25cm

Question 39

THE EYE

Why does the lens change shape?

Answer 39

To focus light from objects at varying distances

Question 40

Where are images formed?

Answer 40

On the retina, which is covered in light sensitive cells

Question 41

Whats the furthest distance the eye can focus on comfortably?

Answer 41

Infinity

Question 42

What’s the shortest distance the eye can focus on comfortably?

Answer 42

Approx 25cm