Medical Applications in Physics

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  • Created by: Hope
  • Created on: 19-04-14 17:22
What are Xrays?
Electromagnetic, transverse waves
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What are xrays apart of and what does this mean about them?
They are apart of the electromagnetic spectrum and this means they transfer energy
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What are the properties of Xrays?
Short wavelength, cause ionisation, Turn photographic film black, are absorbed by metal and bone and are transmitted by healthy tissue
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Define: Ionisation
Adding or removing electrons in atoms or molecules
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How do Xrays show up on photographic film?
They are transmitted through the body, except in areas where they are absorbed by bones, and so the film stays white where the xrays havent hit it
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What is a CCD?
Its what modern xray machines use to form images electronically
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What are CT scans?
They are like xrays but build 3D images of the body
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Complete this sentence: Low doses of xrays may....
Cause cancer
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Complete this sentence: High doses of xrays may....
Kill cancer cells
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What is radiotherapy?
The use of xrays to target cancer cells and cause so much damage to them that the cells die
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Name 4 precautions people must take with xrays
Patients can only have a certain number of xrays, Sheilded walls containing led, Only radiographers can do xrays and they must wear led aprons
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What is the range of human hearing?
20Hz to 20,000Hz
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Complete this sentece: Ultrasound waves are partially..
Reflected when they meet a boundry between two different media with different densitys
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What is important to remember when doing calculations for distance travelled by ultrasound?
The waves always travel there and back so you always have to divide it by 2
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What are 2 uses of Ultrasound?
Medical imaging and removing kidney stones
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How do ultrasound machines get picture of developing babies in the womb?
The ultrasound directed at the body will be partially reflected at the boundry between muscle and skin
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How do ultrasound waves help with the removal of kidney stones?
High frequency ultrasound waves are focused at a kidney stone which makes it break into small enough peices to pass through urine
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Compare how safe ultrasound, xrays and ct scans are..
Ultrasound waves are completely safe, xrays can cause cancer and ct scans can be even more harmful that xrays
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Compare the image quality of ultrasound, xrays and ct scans...
Ultrasound images are fuzzy, Xrays make clear imagines of bones but nothing else and CT scans give high resolution images
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Define: Refraction
The change of direction of light as it passes from one medium to another
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What does the change in density in refraction do to the wave?
Changes the speed/Slows it down
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What is the normal line?
An imaginary line that is 90 degrees on the surface (across the middle)
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What is the angle of incidence?
The angle in which the light ray hits the prism compared to the normal line
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What is the angle of refraction?
The angle at which the light ray inside the prism is compared to the normal line
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Define: Lens
A transparent block that causes light to refract to form an image
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What are the two types of lenses?
Converging and Diverging
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Explain what happens in a converging lens
The converging lens has two parralel light rays, when they hit the lens they refract and they will meet at the principal vocus
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What is the principal focus?
The bit at which the two light rays meet
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What is the focal length?
The distance between the principle focus and the lens
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What are the 3 characterists of a magnifying glass?
Virtual, Upright and Magnified
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What is the equation of magnification?
Image height divided by object height
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Explain what happens in diverging lenses
When the parralell light hits the lens the light rays spread apart
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How do you find the principle focus on a diverging lens?
You imagine the light rays carry on behind the lens until they join together
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On ray diagrams, what is the object shown as?
An arrow
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What happens in lenses when the two rays meet?
An image is formed
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What are the 3 things an image could be discribed as?
Magnified or diminished, Upright or inverted, Real or Virtual
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If an image appeared to be smaller than the object what would it be described as?
Diminished
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If an image was pointed in the same direction as the object what would it be discribed as?
Upright
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If an image was on the same side of the lens as the object what would it be described as?
Virtual
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What are the 7 parts of the eye?
Cornea, Iris, Pupil, Lens, Ciliary Muscles, Suspensory Ligaments, Retina
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What is the function of the cornea?
Refracts light as it enters the eye
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What is the function of the iris?
Controls how much light enters the pupil
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What is the function of the pupil?
Allows light to pass through as it enters the eye
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What is the function of the lens?
Refracts light to focus it onto the retina
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What is the function of the ciliary muscles>
Adjusts shape of lens to make it more or less curved
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What is the function of the suspensory ligaments?
Slackens or stretches to adjust thickness and curvature
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What is the function of the retina?
It contains light receptors which trigger electrical impulses to be sent to brain when light is detected
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Define: Accomodation
The eye can alter the shape and curvature of the lens to adjust the degree of refraction
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If an object was near the eye what would the eye do to focus on the object?
The ciliary mucles would contact, the suspensory ligaments would slacken, the muscle tension on the lens would be low and the lens would be fat and curved
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If an object was far away from the eye what would the eye do to focus on the object?
The ciliary muscles would relax, the suspensory ligaments would be stretched, the muscle tension on the lens would be high and the lens would be thin and less curved
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What is the near point?
The closest an object can be from the eye without the image being blurred
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What is the far point?
The furthest an object can be from the eye without the image being blurred
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What is a normal persons near point?
25cm
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What is a normal persons far point?
Infinity
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What can short sightedness be caused by?
The eyeball being longated or the lens being too thick and cuved
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What would happen if they eyeball was elongated?
The distance between the lens and retina would be too great
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What would happen if the lens was too thick and curved?
The light would be focused infront of the retina instead of onto it
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What can short sightedness be corrected by?
Placing a diverging lens infront of the eye
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What is longsightedness caused by?
The eyeball being too short or the loss of elasticity in the lens
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What can happen if the eyeball is too short?
The distance between the lens and the retina would be too great
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What can happen if the elasticity is lost in the lens?
It cannot become to fat to focus and so the lens
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What is the result of the eyeball being too short and the elasticity being lost in the lens?
The lens would focus light behind the retina instead of onto it
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How can long sightedness be corrected?
By putting a converging lens infront of the eye
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In the equation for the power of a lens, what is the unit for power?
Dioptres = D
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In the equation for the power of a lens, what is the unit for focal length?
Metres = M
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Complete this sentence: In the answer for power of a lens a convex/converging lens will always be...
Positive
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Complete this sentence: In the answer for power of a lens a concave/diverging lens will always be...
Negative
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What can focal length be affected by?
The curvature of the lens and the refractive index of a material
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How can you change the curvature of a lens?
A thicker lens
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How would you make a surface with a higher refractive index have the same focal length as one with a lower refractive index?
Make it thinner
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What can lasers be used for?
Cutting, caustering and burning
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What is a critical angle?
Where the reflected ray disappears
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What is total internal reflection?
When no refraction occurs do to the angle of refraction passing the critical angle
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What is an optical fibre?
A thin rod of high-quality glass
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What do optical fibres do?
Passes light through by total internal reflection until it emerges at the other end
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What can optical fibres be used for?
Endoscopes and high speed communications
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Other cards in this set

Card 2

Front

What are xrays apart of and what does this mean about them?

Back

They are apart of the electromagnetic spectrum and this means they transfer energy

Card 3

Front

What are the properties of Xrays?

Back

Preview of the front of card 3

Card 4

Front

Define: Ionisation

Back

Preview of the front of card 4

Card 5

Front

How do Xrays show up on photographic film?

Back

Preview of the front of card 5
View more cards

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