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Physics > P3.1 (Medical applications of physics) ( up to lenses) > Flashcards

P3.1 (Medical applications of physics) ( up to lenses) Flashcards

1
Q

Relative to visible light, do X - rays have a short or long wavelength?

A

X- rays have a SHORT wavelength

only shorter waves = gamma rays

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2
Q

What type of waves are X-rays?

A
  • TRANSVERSE WAVES

oscillations go up and down/ perpendicular to energy transfer

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3
Q

What is ionisation?

A

Adding or removing electrons from atoms

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4
Q

What are the useful properties of X-rays?

A
  • Absorbed by metal and bone (hard tissue)
  • Pass through healthy / soft tissue
  • Atom sized wave length (VERY SHORT)
  • Affect photographic film (turns black) just like visible light
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5
Q

How can X-rays help identify broken bones and objects within the body?

A
  • White photographic film is placed behind patient
  • When the x-rays are passed through area of concern, rays are absorbed by bones and hard tissue
  • The remaining rays pass through and turn the paper black
  • This leaves white area where broken bones can be identified
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6
Q

How can X-rays be used to identify healthy and decaying teeth?

A

Decayed teeth do not absorb X-rays as well as healthy teeth so where the teeth are decayed, the paper will be darker

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7
Q

How do modern X-rays work without photographic paper?

A

Modern X-rays use CCDs (Charge Coupled Devices) in order to produce images electronically so they are more easily stored and shared

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8
Q

What are the benefits of CT scans over X-rays?

A

CT scans take multiple images to produce a 3D image that can be manipulated and viewed from more angles to identify further issues

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9
Q

What are negative side effects of X-rays?

A
  • As they are IONISING, they can damage DNA in cells

- Although high doses of X-rays can kill cancer, low doses can cause it

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10
Q

How are X-rays used to treat cancerous cells in radiotherapy?

A
  • High energy X-rays are directed at the cancerous cells

- This causes damage to the point of death of the cells

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11
Q

What substance can be used to protect radiographers from damage due to X-rays?

A

Lead
such as
Lead aprons
Lead barriers

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12
Q

What is the range of human hearing?

A

20 - 20,000 hz

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13
Q

Why can humans not hear ultrasound?

A

Ultrasound has a frequency of around 20,000 hz which is above the human range of hearing

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14
Q

How do ultrasounds produce images of inside the body?

A
  • The ultrasound rays enter the body
  • When the ray meets a boundary of two different densities, some of it is reflected back
  • A device receives these reflected rays and produces an image from them
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15
Q

What calculation measures the distance travelled by an ultrasound ray?

A

S = V x T

Distance (m) = Speed x Time

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16
Q

How can ultrasounds be used outside of medicine?

A

For quality control in products (eg metals) to check for cracks

17
Q

How are ultrasounds used in medicine?

A

To monitor a baby’s growth

To treat kidney stones

18
Q

What are kidney stones?

A

Solid crystals formed in urine that can pass into the ureter and block it causing immense pain

19
Q

How can ultrasounds treat kidney stones?

A

A high frequency ultrasound is directed into the kidney stone causing it to vibrate and shatter into smaller pieces

20
Q

How are X-rays and ultrasounds different?

A
  • X-rays have a shorter wavelength allowing them to provide more detailed imagery in order to identify small fractures
  • CT scans also produce extremely detailed imagery
  • Ultrasound waves are non ionising and safe to be exposed to a number of times
21
Q

What is refraction?

A

The change of direction of light as it passes through two substances of different densities

22
Q

What happens to the speed of light when it enters a DENSER substance?

A

It SLOWS DOWN

Causing it to bend TOWARDS the normal

23
Q

At what angle does refraction not happen?

A

If the light ray hits the object at 90degrees, it will not be refracted and will continue in a straight line

24
Q

What is the refractive index?

A

The refractive index is the capability of an object to slow the speed of light
It is a RATIO rather than a measurement

25
Q

How do you calculate the refractive index of a material?

A

Sin i (Angle of incidence) / Sin r (Angle of refraction)

26
Q

Which direction does the glass bend in a CONVERGING lens?

A

The sides of the lens bend OUTWARD

It is represented by a line with arrows facing outwards

27
Q

Which direction do converging lenses bend light?

A

Inwards to a focal point

28
Q

How is the glass of a diverging lens arranged?

A

The glass bends INWARDS

It is represented with a vertical line with two arrows pointing inwards

29
Q

What factors can be used to describe an image?

A
  • Magnified / diminished
  • Upright / inverted
  • Real / Virtual
30
Q

How do you calculate the ratio of magnification?

A

Magnification = Image height / Object height

Physics (18 decks)

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