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Physics (P.3) > Medical Applications Of Physics > Flashcards

Medical Applications Of Physics Flashcards

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1
Q

What are X-rays?

A

They are part of the electromagnetic spectrum. They have a short wavelength and cause ionisation

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2
Q

What are the properties of x-rays?

A

They affect a photographic film in the same way as light
They are absorbed by metal and bone
They are transmitted by soft tissue
Their wavelength is of the same order of magnitude as the diameter if an atom

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3
Q

What can x-rays be used for?

A

To diagnose and treat some medical conditions
e.g. CT scans, bone fractures, dental problems and killing cancer cells
The use of CCDs allows images to be formed electronically

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4
Q

Using what machines should we take precautions around?

A

X-ray machines and CT scanners

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5
Q

What cab electronic systems be used to produce?

A

ultrasound waves, which have a frequency higher than the upper limit hearing for humans

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6
Q

what is the human hearing range?

A

20Hz to 20, 000Hz

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7
Q

Talk about how ultrasound waves reflect.

A

Ultrasound waves are partially reflected when they meet a boundary between two different media.
The time takes for the reflection to reach a detector can be used to determine how far away such a boundary is

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8
Q

What can ultrasound waves be used for?

A

They can be used in machines, such as:

pre-natal scanning and the removal of kidney stones

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9
Q

What is refraction?

A

It is the change of direction of light as it passes from one medium to another

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10
Q

How does a lens form an image?

A

By refracting light

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11
Q

What is a convex lens?

A

One which bends outwards

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12
Q

What is a concave lens?

A

One which bends inwards

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13
Q

What is brought to focus at the principle focus?

A

In a convex or concave lens, parallel rays of light

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14
Q

What si the nature of an image defined by?

A

by its size relative to the object
whether it is upright or inverted relative to the object
whether it is real or virtual

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15
Q

What is another way of saying concave lens?

A

diverging

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16
Q

what is another way of saying a convex lens?

A

converging

17
Q

What is the retina and what does it do?

A

It is a layer which contains cells sensitive to light, which triggers nerve impulses that pass via the optic nerve of the brain, where a visual image is formed

18
Q

What is the cornea?

A

It is the transparent layer formed at the front of the eye

19
Q

What is the iris?

A

It is the colour part of the eye

20
Q

What does the ciliary muscle do?

A

It causes changes in the shape of the lens, which allows the light to be focused at varying distances

21
Q

What is the fovea?

A

Where the clearest image is

22
Q

What does the pupil do?

A

It determines how much light is let into the eye

23
Q

What does the suspensory ligament do?

A

It links the ciliary muscle and lens, and holds the lens in place

24
Q

What is long sight caused by?

A

It is caused by the eyeball being too short, or the eye lens being unable to focus

25
Q

What causes short sight?

A

It is caused be the eyeball being too long, or the eye lens being unable to focus

26
Q

If an object is distant what does the eye do?

A

Ciliary muscles relaxes
Suspensory ligaments stretches
The shape of lens is thin and less convex

27
Q

If an object is near what does the eye do?

A

Ciliary muscles contracts
Suspensory ligaments slackens
The shape of lens is fat and more convex

28
Q

How can short sight be corrected?

A

By placing a concave lens in front of the eye

29
Q

How can long sight be corrected?

A

By placing a convex lens in front of the eye

30
Q

What can an eye focus on?

A

a near point (approximately 25 cm) and the far point (infinity)

31
Q

What does a lens in a camera do and what is the similar role in the eye?

A

To focus light onto the photosensitive surface at the back of the camera. This can either be photographic film or a CCD (charge-coupled device).

Eye: Lens - which focuses light onto the retina.

32
Q

What does a focusing screw in a camera do and what is the similar role in the eye?

A

Allows the user to adjust the focus for nearer or more distant objects.

Eye: Ciliary muscles - which stretch or slacken the suspensory ligaments to adjust the shape of the lens

33
Q

What does an aperture in a camera do and what is the similar role in the eye?

A

Allows the user to adjust the amount of light entering the camera in different light conditions.

Eye: Iris - which adjusts the amount of light entering the eye through the pupil.

34
Q

What does a shutter in a camera do and what is the similar role in the eye?

A

Allows the user to adjust the length of time that light enters the camera, which controls the amount of light to which the photosensitive surface is exposed.

Eye: Not applicable (although we do have eyelids).

35
Q

What does a photosensitive surface in a camera do and what is the similar role in the eye?

A

Detects and records the light which is focused onto it. This can be on photographic film, but digital cameras use CCDs which convert light into electrical signals which can be stored.

Eye: Retina - which detects light and converts it into electrical impulses which are sent to the brain.

36
Q

What is the focal point of a lens determined by?

A

The refractive index of the material from which the lens is made
The curvature of the two surfaces of the lens

37
Q

For a given focal length, the greater the refractive index, the … the lens. What does this mean?

A

Flatter

This means that the lens can be manufactured thinner

38
Q

what can be sent along optic fibers?

A

Visible light

e.g. endoscope for internal imaging

39
Q

What is a laser used for?

A

As an energy source for cutting, cauterising and burning

Physics (P.3) (7 decks)

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