Health Physics

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Health Physics
2011-01-30 14:19:41
Physics Health Physics

Standard Grade Physics - Health Physics
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  1. Define temperature
    The temperature of an object is a measure of how hot or cold it is.
  2. What is the unit for temperature?
    Degrees celcius (°C)
  3. What do we measure temperature with?
    A thermometer
  4. Name three different types of thermometers
    • Liquid in glass
    • Liquid crystal
    • Digital (thermistor) thermometer
    • Rotary (bimetallic strip)
    • Thermocouple
  5. Explain what is special about the tube inside the clinical liquid in glass thermometer?
    A clinical liquid in glass thermometer will have a "kink" to prevent the liquid falling
  6. Give three differences between a clinical liquid in glass thermometer and an ordinary liquid in glass thermometer
    • The scale is smaller on a clinical liquid in glass thermometer (35 - 42 °C) than an ordinary liquid in glass thermometer
    • A clinical thermometer is more sensitive (as it has small divisions of 0.1 °C) than an ordinary liquid in glass thermometer
    • In a clinical liquid thermometer ther reading sticks at the highest value because the mercury inside breaks when measured from the patient
  7. Sound can travel through....?
    • Solid
    • Liquid
    • Gas
  8. Sound cannot travel through....?
    A vacuum
  9. How does a stethoscope work?
    Sounds picked up at the chestpiece are transmitted up the air in the tubing to the earpieces
  10. What is a humans range of hearing?
    20 Hz - 20 000 Hz (decreasing with age)
  11. High frequency vibrations beyond the range of human hearing (abovve 20 000 Hz) are called _________?
  12. Describe how ultrasound is used to obtain images of a baby in its mother's womb
    • The waves are emitted by a probe and reflected by tissues and bones of the foetus from different depths, so a 3D picture can be built up
    • Jelly or oil is placed between the probe and the skin. This excludes the air to prevent the ultrasound being reflected at the change from air to tissue. The waves would then not enter the woman's body
    • The reflected waves are detected and the patterns of reflection times are used to build up an image on a computer monitor
  13. Light travels in straight lines called ____?
  14. When light passes from one material into another of different density, its shape changes and so its direction changes - this is known as ________?
  15. Convex lenses have a _______ power?
  16. Concave lenses have a _______ power?
  17. What is the formula for focal length?
    P = 1/f
  18. The image of an object formed on the retina is ______ _____ and ______ ______?
    • upside down
    • laterally inverted (back to front)
  19. To correct long sight a ______ lens is placed in front of the eye?
  20. To correct short sight a ________ lens is placed in front of the eye?
  21. Light passes along an optic fibre by......?
    total internal reflection
  22. Fibre optics can be used to transfer _____ light into the body?
  23. Give three uses of lasers in medicine
    • Laser eye surgery
    • Laser scalpel
    • Vaporising Cancer Tumors
    • Removing Tattoos/Birth Marks
  24. Name one use of infra-red in medicine
    • Detect cancerous tissue
    • To help heal injured muscles
  25. Name one use of ultraviolet in medicine
    • To sterilise hospital equipment
    • To treat Vitamin D deficiency and some skin disorders
  26. Too much exposure to ultraviolet radiation can be harmful because......?
    it can cause sunburn and even skin cancer
  27. Name one use of x-rays in medicine
    • To see inside people
    • To kill cancer tumours (in high doses)
  28. Describe how photographic film can be used to detect x-rays
    Photgraphic film goes dark where x-rays hit. This leaves white patches on the film where the bones were in the way
  29. Describe how computerised tomography or a CAT scan works
    • Using a special X-ray machine which rotates around the body, x-ray images of the body are taken in thin slices.
    • A computor combines all these images to provide a three - dimensional picture of the body
  30. Radioactivity can knock electrons out of atoms. This is known as _____?
  31. Name the three types of radioactivity
    • Alpha (α)
    • Beta (β)
    • Gamma (γ)
  32. How far can alpha radiation travel and what is it stopped by?
    • A few cm
    • Paper
  33. How far can beta radiation travel and what is it stopped by?
    • Metres
    • A few mm of aluminium
  34. How far can gamma radiation travel and what is it stopped by?
    • Infinite (∞)
    • Lead
  35. What is the unit of dose equivalent?
    Sieverts (Sv)
  36. What type of radiation causes the most ionisation?
    alpha (α)
  37. What does dose equivalent take into account?
    • The type of radiation
    • The energy of radiation
  38. The biological effect of radiation depends on.....?
    The dose equivalent and the type of tissue absorbing the radiation
  39. State the meaning of the term half-life
    The time for a radioactive substance's activity to decrease by 50%
  40. What is activity measured in?
    Becquerels (Bq)