Physics GCSE P1B
- Created by: Katy Head
- Created on: 16-05-11 10:45
RADIATION WE USE
- On the move - Short radio waves from a satellite to GPS (TomTom)
- Fixing a fracture - X-rays to show doctors what is needed
- Hubble Space telescope - For almost 20 years this has been orbiting the earth - pictures sent back by radio waves
- Mobile Phone - Mobile phone masts
- The Sun is a star - this makes its own light
- The Earth is a planet - light is reflected from sun
- The Moon is a satellite - light is reflected from sun
The VISIBLE light spectrum ROYGBIV - light that has all colours - known as white light
White light is reflected by a mirror
Light travels in straight lines
The Electro-magnetic Spectrum
Electro-magnetic waves are electric and magnetic disturbances that transfer energy from one place to another
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One wavelength is the distance from peak to peak
Frequency = Number of complete waves passing a point each second
The unit of frequency = Hertz
- (Hz) - 1 Hertz = 1 waves per second
- (KHz) - 1 Kilohertz = 1000 waves per second
- (MHz) - 1 Megahertz = 1 million waves per second
EQUATION -
Wavespeed (metres per second) = Frequency (Hz) * Wavelength (metres)
so
Wavelength = Wavespeed
Frequency
and
Frequency = Wavespeed
Wavelength
All waves travel at a speed of 300 million metres per second through space or a through a vacuum
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Remember the order of the Electro-magnetic spectrum - Shortest to Longest
- Gamma Rays
- X-rays
- Ultra Violet
- Visible Light
- Infra-red
- Microwaves
- Radio waves
GAMMA RAYS AND X-RAYS
- X-rays and Gamma Rays radiation are absorbed by dense materials in bone and in metal
- X-rays and Gamma Rays radiation damages living tissue when they pass through it
- X-rays are used in hospital to take radiographs - they pass through the soft tissue but are absorbed by the bone and thick metal plates
- Gamma Rays are used to:-
- kill harmful bacteria in food
- sterilise surgical equipment
- kill cancer cells
Remember how Gamma Rays are used to cure cancer -
- Cobalt 60 source for the Gamma rays
- Contained in lead container
- Rays leave chamber through exit channel
- Rays are directed to the the cancerous Tumour from a number of directions
LIGHT AND ULTRAVIOLET RADIATION
- Ultraviolet radiation is in the electro-magnetic spectrum between visible light and Xrays
- Ultraviolet radiation has a shorter wavelength than light
- Ultraviolet radiation is harmful to the skin and the eyes
****** look at the diagram on page 82 in AQA text book ******
UV is harmful to the skin and the eyes because:-
- Wavelengths are shorter than light
- UV carries more energy than light waves
- too much UV causes sunburn and can cause cancer
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How Electro-magnetic waves react with substances
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Reflected waves :-
- Some or all waves may be reflected…
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