Flashcards
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Flashcards do conjunto (50)
- 1what is a CCD?a charge-coupled device
- 2what materials absorbs x-rays?bones and metal
- 3what materials do x-rays pass through?healthy tissue
- 4why are CT scans only used when really necessary?they use very high doses of radiation
- 5uses for x-rays?diagnosing medical conditions
treating cancer - 6why can x-rays be used to treat cancer?x-rays cause ionaisation so high doses will kill living cells
- 7how do they treat cancer?1)focused on tumour using wide beam 2)beam rotated 3)minimises exposure to normal cells
- 8what precautions can radiographers to minimise radiation dose?lead aprons, lead screen or leave the room
- 9what is ultrasound?high frequency waves- 20,000Hz
- 10what happens to ultrasound waves at boundaries?waves get partially reflected
- 11what can you use to find boundaries?oscilloscope
- 12ultrasound at boundaries?some is reflected and some passes through
- 13uses of ultrasound?breaking down kidney stones
pre-natal scanning
diagnosing heart problems - 14how can ultrasound be used for pre-natal scanning?ultrasound passes through the body but when they reach the boundary, some is reflected back and detected
- 15how can ultrasound be used to break down kidney stones?a beam concentrates high energy waves at the stones and turns them into sand like particles
- 16is ultrasound safe?non ionising(safe). x-rays are ionising and CT scans use lots of radiation.
- 17is ultrasound image quality good?ultrasound images are fuzzy, x-rays are clearer of bone/metal, CT scans are detailed and 3D
- 18why does refraction occur?waves changing speed as they travel through different media.
- 19what happens when waves go from a dense material to a less dense material?they speed up and bend away from the normal
- 20what happens when waves go from a less material to a more dense material?the slow a down and bend towards the normal.
- 21what is the formula to calculate the formula for refractive index?sin i/sin r
- 22which lens makes parllel rays of light move together?convex or converging lens
- 23which lens causes parallel rays of light to move apart?concave or diverging
- 24what is the line called that passes through the middle of the lens?axis
- 25what is the focal length?the distance from the centre of the lens to the principal focus
- 26what is a real image?an image that can be projected on to a screen
- 27what is a virtual image?an image made from dashed construction lines, cant be projected on to a screen
- 28what are the words that can be used to describe an image?real/virtual
upright/inverted
enlarged/diminished - 29what image does a diverging lens always produce?a virtual image
- 30what lens does a magnifying glass use?a converging lens
- 31what is the formula for calculating magnification?image height/object height
- 32what is the formula for calculating power?1/focal length
- 33what is the unit for power?dioptres
- 34for a converging lens, is the power positive or negative?positive
- 35for a diverging lens, is the power positive or negative?negative
- 36function of the cornea?does most of the eye's focusing
- 37function of the iris?controls the size of the pupil
- 38function of the pupiol?lets light in, controls the intensity of the light entering the eye
- 39function of the lens?changes shape to focus light on objects at varying distances
- 40function of the retina?light-sensitive cells detect light and send signals to the brain
- 41function of the ciliary muscles?controls shape of the lens. contract=makes lens fat. relax=lens thins and flattens
- 42function of suspensory ligaments?connected to the ciliary muscles to change the shape of the lens
- 43near and far points?near point= 25cm (approx)
Far point= infinity - 44similarities between a camera and an eye?1)convex lens
2)retina is the same as film/CCD - 45which lens corrects short sight?diverging lens
- 46which lens corrects long sight?converging lens
- 47what is short sight?cant focus on distant objects. eye ball is too long. images formed infront of retina
- 48what is long sight?cant focus near objects. eye ball is too short. images focus behind the retina
- 49how does laser eye surgery work?a laser is used to change the shape of the cornea to increase or decrease power
- 50uses for lasers?cauterise blood vessels, burn off scarred skin, cut through tissue without a scalpel
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- FlashCards sobre Sem título, criado por chloenewton em 23-04-2014.
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- chloenewton
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