Medical applications of physics

Question 1

X-rays have a short wavelength and high…

Answer 1

…frequency.

Question 2

True or false, X-rays are not ionizing.

Answer 2

False, the cause ionisation.

Question 3

Properties of X-rays:

Answer 3

Effect photographic film in the same way as light.
Absorbed by metal and bone.
Transmitted by soft tissue
Wavelength same order of magnitude as an atom.

Question 4

Uses of X-rays in medicine:

Answer 4

CT scans: fractures, dental problems.
Killing cancer cells.
Treating diseases.

Question 5

How can X-ray images be formed without a photographic film?

Answer 5

The use of CCDs (Charged-Coupled Devices) forms an electronic image.

Question 6

True or false, X-rays are dangerous so precautions must be taken into account when using.

Answer 6

True.

Question 7

What is the frequency of ultrasound?

Answer 7

Any frequency above 20,000Hz.

Question 8

What is the range of frequency humans can hear?

Answer 8

20Hz to 20,000Hz.

Question 9

What is the definition of ultrasound?

Answer 9

A sound with a frequency higher than the upper limit of the human hearing range.

Question 10

What happens when ultrasound reaches a boundary between two different media?

Answer 10

Some is reflected.

Question 11

How can the reflections of ultrasound be used to determine distance?

Answer 11

The time taken for reflections to reach a detector can how far away a boundary is.

Question 12

What is the equation for calculating distances between inferences?

Answer 12

s = vt

Where:
s is distance in metres
v is speed in m/s
t is time in s

Question 13

How can ultrasound be used in medicine?

Answer 13

Pre-natal scanning.

Removal of kidney stones.

Question 14

Refraction is what?

Answer 14

The change in direction of light when it passes from one medium to another.

Question 15

A lens forms a what by refracting light?

Answer 15

An image.

Question 16

What is a principle focus?

Answer 16

When parallel rays of light travelling through a convex lens and are brought to a focus.

Question 17

The distance from the lens to the principle focus of it is known as what?

Answer 17

The focal length.

Question 18

Equation for refractive index?

Answer 18

N = sin i / sin r

Where:
N is refractive index
i is angle of incidence
r is angle of refraction

Question 19

The nature of an image is defined how?

Answer 19

By its relative size to the object.
Whether it is upright or inverted.
Whether it is real or virtual.

Question 20

What lenses are used in magnifying glasses?

Answer 20

Converging.

Question 21

Magnification is calculated how?

Answer 21

Magnification = image height / object height

Question 22

Name the 6 parts of the eye:

Answer 22

Retina.
Pupil / iris.
Cornea.
Lens.
Ciliary muscle.
Suspensory ligaments.

Question 23

Convex and concave lenses can be used to correct what problems with vision?

Answer 23

Long-sightedness caused by the eyeball being too short or the lens being unable to focus.
Short-sightedness caused by eyeball being too long or lens being unable to focus.

Question 24

What words can be used to describe range of vision?

Answer 24

Near point and far point.

Question 25

What distance is a human’s near point?

Answer 25

Approximately 25cm.

Question 26

What is meant by near point?

Answer 26

The closest an object can be to the eye and still be in focus.

Question 27

What distance is a human’s far point?

Answer 27

Infinity.

Question 28

What is meant by far point?

Answer 28

The furthest an object be can and still be in focus.

Question 29

In a camera, what is the equivalent of the retina?

Answer 29

A film or CCD.

Question 30

Equation for calculating the power of a lens:

Answer 30

P = 1/f

Where:
P is power in D
f is focal length in m

Question 31

The focal length of a lens is determined by what?

Answer 31

The curvature of the lens and the refractive index from which it is manufactured.

Question 32

How can manufacturers make thinner lenses when given a set focal length?

Answer 32

They can increase the refractive index of the lens with a different material and decrease the curvature to make a thinner lens with the same focal length.

Question 33

What is total internal reflection?

Answer 33

When light enters an object beyond the critical angle of the medium so is reflected internally.

Question 34

Equation for refractive index using critical angle of a medium:

Answer 34

N = 1 / sinc

Where:
N is refractive index.
c is critical angle.

Question 35

Uses of total internal reflection in medicine:

Answer 35

Visible light can be sent along optical fibres in an endoscope to see inside patients.

Question 36

Briefly how does laser eye surgery work?

Answer 36

A laser is used as an energy source for cutting, cauterising and burning parts of the eye into certain shapes.