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Flashcards

P3

hana javed Inglês 39 flashcards

Flashcards do conjunto (39)

  1. 1How can X-Rays treat cancer?High doses of X-Rays can kill living cells
    •X-Rays are focused on the tumour using a wide beam
    •The beam is rotated around the patient with the tumour at the centre
    -This minimises the risk to the ready of the body as the normal cells' exposure to radiation is minimised
  2. 2How are X-Rays formed electronically?Using charge coupled devices (CCDs)- silicon chips (about the size of a postage stamp) divided into millions of identical pixels.
    •CCDs detect X-Rays and produce and produce electronic signals to form high resolution images
  3. 3What do the brighter bits on a photograph taken with X-Rays indicate?The brighter bits are where fewer X-Rays get through- negative image. The plate starts off all white and the X-Rays show up black
  4. 4What size (roughly) is the wavelength of an X-Ray?A wavelength is roughly the same size as the diameter of an atom
  5. 5What are X-Rays transmitted and absorbed by?X-Rays are transmitted by (pass through) healthy tissue, and are absorbed by dense materials such as bones and metal
  6. 6What are X-Rays?X-Rays are high frequency, short wavelength, electromagnetic waves
  7. 7What are CT scans?Computerised axial tomography scans- they produce images of soft and hard tissue
  8. 8What is the process of a CT scan?Patients are put inside the cylindrical scanner and an X-Ray is emitted from an X-Ray tube on one side and detected on the other , The X-Ray tube and detectors are rotated around the person so a 3D image can be formed
  9. 9How do radiographers minimise their exposure to X-Rays?The wear lead aprons, stand behind a lead screen, or leave the room
  10. 10What is ultrasound?A sound with a higher frequency than we can hear
  11. 11When are ultrasound waves partially reflected?When a wave passes from one medium into another- some is reflected off the boundary between the two media, and some is transmitted (+refracted)
  12. 12How is ultrasound used for Pre-natal scanning of a fetus?When the waves meet a boundary between two different media, (fluid in the womb and the skin of the fetus) some of the wave is reflected back. The exact timing and distribution of these echoes are processed by a computer to form an image
  13. 13What are disadvantages to CT scans?They use a lot more X-Ray radiation- exposed to more ionising radiation
  14. 14Why are ultrasound waves used for scanning of fetus even though they produce fuzzier images than X-Rays?X-Rays are ionising and cancer causing- not safe to use on developing babies
  15. 15What can X-Rays produce clear images of?Bones and metal
  16. 16What kind of images can CT scans produce?•Detailed images- useful to diagnose complicated illnesses
    •High quality 3D images- can be used in the planning of complicated surgery
  17. 17What is refraction caused by?Waves changing speed (as a result, the wave changes direction when it enters a different medium)
  18. 18What happens when waves slow down?They bend towards the normal
  19. 19What happens when light enters glass or plastic?It slows down to about 2/3 of its speed in air
  20. 20What happens if a wave hits a boundary at 90 degrees (i.e.along the normal)?It will carry on in the same direction, but slow down
  21. 21What can partial reflection of ultrasound waves be used for?Can be used to measure how far away a boundary is- the time it takes for the reflections to reach a detector shows how far away it is- ultrasound imaging
  22. 22How can oscilloscope traces be used to find boundaries?It can show an ultrasound pulse reflecting off two separate boundaries. The "seconds per division" setting means you can work out the time between pulses by measuring on the screen. Knowing the speed of sound, you could work out the distance between boundaries (d=s x t)
  23. 23How can ultrasound be used to break down kidney stones?The ultrasound beam concentrates high energy waves at the kidney stone and turns it into sand-like particles that pass out of the body in the urine
  24. 24What happens when light hits a different medium?Some light passes through but some will be reflected (depending on the angle of incidence)
  25. 25What is refractive index?The refractive index of a medium is the ratio of speed of light in a vacuum to the speed of light in that medium
  26. 26When an incident ray passes from air into another material, the angle of refraction of the ray depends on...?The refractive index of the material
  27. 27What is the formula for refractive index?Refractive index= (Sin x angle of incidence) / Sin x angle of refraction
  28. 28What is a converging lens?It is convex- bulges outwards
  29. 29What does a converging lens do to parallel rays of light?It causes them to converge (move together) at the principle focus
  30. 30What is a diverging lens?A concave lens- caves inwardly
  31. 31What does a diverging lens do to parallel rays of light?It causes them to diverge (spread out)
  32. 32What is the axis of a lens?A line passing through the middle of the lens
  33. 33Where is the principle focus of a converging lens?Where rays hitting the lens parallel to the axis all meet
  34. 34Where is the principle focus of a diverging lens?The point where rays hitting the lens parallel to the axis appear to come from
  35. 35What are the three rules for refraction in a converging lens?1. An incident ray parallel to the axis refracts through the principle focus on the other side
    2. An incident ray passing through the principle focus refracts through the lens and travels parallel to the axis
    3. An incident ray passing through the centre of the lens carries on in the same direction
  36. 36What are the three rules for refraction in a diverging lens?1. An incident ray parallel to the axis refracts through the lens, and travels in line with the principle focus
    2. An incident ray passing through the lens towards the principle focus refracts through the lens and travels parallel to the axis
    3. Am incident ray passing through the centre of the lens carries on in the same direction
  37. 37What is a real image?An image that occurs when the light from an object comes together to form an image on a 'screen'- like the image formed on an eye's retina
  38. 38What is a virtual image?When the rays are diverging, so the light appears to be coming from a different place
  39. 39How do you draw a ray diagram for an image through a converging lens?1. Pick a point on the top of the object and draw a ray to the lens, parallel to the axis
    2. Draw another ray from the top of the object going right through the middle of the lens
    3. The incident ray parallel to the axis is refracted through the principle focus
    4. The ray passing through the middle of the lens does not bend

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FlashCards sobre P3, criado por hana javed em 23-03-2017.
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hana javed
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