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Temperature
Measure of hotness / coldnessDegrees Celcius ( 0 C ) ThermometerAll thermometers have a property that
changes with temperatureBody Temp : 370CGood Indicator of Health
Sound
Range of hearing 20 - 20000 Hz80dB danger level : food mixerStethoscope acts as hearing aidUltrasound : > 20000 HzUsed to ‘see’ inside body e.g scan womb of
pregnant woman
Light / Eye
Refraction : Light changes speed when it travels from one medium to another
Slows down : bends towards the normalSpeeds up : bends away from the normal
AirGlass
Angle of Refraction
Angle of Incidence
The Eye
Image is Inverted, Diminished and Laterally Inverted
The cornea and lens act together to focus the light.
The EyeDistant objects;parallel rays of light; low power lens
Close up objects;rays of light spread out;high power lens
Long Sight
Distant objects are in focus Close up objects are blurredThey are brought to a focus behind retinaConvex lens is placed in front of eye
Short Sight
Close up objects are in focusDistant objects are blurredBrought to a focus in front of retinaConcave lens is placed in front of eye
Fibrescope
Fibre Optics : used to see inside bodyOne bundle carries light into bodyOther bundle carries reflected light back to
eye of doctor / nurseCold light source used
Infra - Red Radiation
I.R. used to treat muscle strainsHot objects give out I.R.Cancerous cells are warmer than
surrounding healthy ones :show up on thermogram
Ultra Violet Radiation
Needed to produce essential vitamins in body
Exposure can lead to skin cancerUsed to treat acne / skin disorders
X Rays
Blacken photographic plateBones absorb x rays but they pass through
skin / muscleCT scan 3D picture built up / allows precise
location of problems
Ionising Radiation
Model of Atom
Protons and neutrons in nucleus
Electrons are around the nucleus somewhere
Number of protons equals number of electrons
Ionising Radiation
Alpha : absorbed by paper / few cms of airBeta : absorbed by thin metalGamma : partially absorbed by lead / concreteIonising Radiation KILLS / Changes living cellsAlpha causes most ionisation : adds or knocks
electrons off atoms forming charged ions
Ionising Radiation
Used to kill bacteria on medical instruments kill cancerous cells trace blood flow around body
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)
t
NA =
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.
Half Life Graph
0
500
1000
1500
2000
2500
0 100 200 300 400
Time (s )
Activ
ity (
MBq
)
Half life is time for activity to fall to half its original value i.e. from 1000 to 500 Bq