Temperature

1
Temperature

• Measure of hotness / coldness
• Degrees Celcius ( 0 C ) Thermometer
• All thermometers have a property that changes
  with temperature
• Body Temp 370C
• Good Indicator of Health

2
Sound

• Range of hearing 20 - 20000 Hz
• 80dB danger level food mixer
• Stethoscope acts as hearing aid
• Ultrasound gt 20000 Hz
• Used to see inside body e.g scan womb of
  pregnant woman

3
Light / Eye

• Refraction Light changes speed when it travels
  from one medium to another
• Slows down bends towards the normal
• Speeds up bends away from the normal

Air
Glass
Angle of Incidence
Angle of Refraction
4
Refraction
5
Focal Length
Focal length, f
6
Convex Lenses
The thicker the lens the more powerful the lens
and the shorter the focal length
7
Concave Lenses
The thicker the lens the more powerful the lens
and the shorter the focal length
8
The Eye
Image is Inverted, Diminished and Laterally
Inverted The cornea and lens act together to
focus the light.
9
The Eye
Distant objectsparallel rays of light low
power lens
Close up objectsrays of light spread outhigh
power lens
10
Long Sight

• Distant objects are in focus
• Close up objects are blurred
• They are brought to a focus behind retina
• Convex lens is placed in front of eye

11
Short Sight

• Close up objects are in focus
• Distant objects are blurred
• Brought to a focus in front of retina
• Concave lens is placed in front of eye

12
Power of Lens
Dioptres, D metres , m
13
Fibrescope

• Fibre Optics used to see inside body
• One bundle carries light into body
• Other bundle carries reflected light back to eye
  of doctor / nurse
• Cold light source used

14
Infra - Red Radiation

• I.R. used to treat muscle strains
• Hot objects give out I.R.
• Cancerous cells are warmer than surrounding
  healthy ones show up on thermogram

15
Ultra Violet Radiation

• Needed to produce essential vitamins in body
• Exposure can lead to skin cancer
• Used to treat acne / skin disorders

16
X Rays

• Blacken photographic plate
• Bones absorb x rays but they pass through skin /
  muscle
• CT scan 3D picture built up / allows precise
  location of problems

17
Ionising Radiation

• Model of Atom

Protons and neutrons in nucleus
Electrons are around the nucleus somewhere
Number of protons equals number of electrons
18
Ionising Radiation

• Alpha absorbed by paper / few cms of air
• Beta absorbed by thin metal
• Gamma partially absorbed by lead / concrete
• Ionising Radiation KILLS / Changes living cells
• Alpha causes most ionisation adds or knocks
  electrons off atoms forming charged ions

19
Ionising Radiation

• Used to
• kill bacteria on medical instruments
• kill cancerous cells
• trace blood flow around body

20
Ionising Radiation

• Nucleus decays( breaks up ) giving out ionising
  radiation
• Activity equals the number of nuclei that break
  up per second.
• Units are Becquerels ( Bq)

21
Ionising Radiation

• Half Life time for Activity to drop to half its
  original value
• Original activity is 100 Bq then after one half
  life the activity will drop to 50Bq. After
  another half life it will drop to 25 Bq and so on.

22
Half Life Graph
Half life is time for activity to fall to half
its original value i.e. from 1000 to 500 Bq
23
Biological effect

• This depends on
• Tissue exposed
• Ionising Radiation exposed to
• Time exposed for
• Energy of ionising radiation
• Called Absorbed Dose units Sieverts (Sv)
• Alpha has greater effect than beta or gamma.