Temperature §Measure of hotness / coldness §Degrees Celcius ( 0 C ) Thermometer §All thermometers have a property that changes with temperature §Body Temp.

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

Refraction

Focal Length

Focal length, f

Convex Lenses

The thicker the lens the more powerful the lens and the shorter the focal length

Concave Lenses

The thicker the lens the more powerful the lens and the shorter the focal length

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

Power of Lens

LengthFocalPower

1=

Dioptres, D metres , m

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

Biological effect

This depends on Tissue exposedIonising Radiation exposed toTime exposed forEnergy of ionising radiation

Called Absorbed Dose : units Sieverts (Sv)

Alpha has greater effect than beta or gamma.