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P1 topic 2
The electromagnetic spectrum
|What do all electromagnetic waves have in common?
|They all travel at 300,000km/s in a vacuum, and they are all transverse
|What is the EM spectrum, in increasing wavelength and decreasing frequency?
|Gamma rays X-rays Ultra-violet rays Visible light Infrared Microwaves Radiowaves
|TRUE OR FALSE: the EM spectrum is continuous.
|TRUE: the spectrum is continuous so all values of wavelength are possible
|Describe in terms of frequency, the dangers of electromagnetic waves.
|The greater the frequency of an EM wave, the more energy it transfers, therefore the more hazardous it is
|What are the dangers and uses of microwaves?
|DANGERS: can heat water, so since 70% of our bodies are made up of water there is a risk of internal heating of body cells USES: satellite transmission, e.g. they can carry TV signals. They also vibrate & heat up molecules so they're used in cooking
|What are the dangers and uses of infrared?
|DANGERS: our skin absorbs IR radiation which we feel as heat, and in large doses it can damage our cells and lead to skin burns USES: TV remote controls and cooking. Since all warm objects give off heat as IR radiation it can be used in thermal imaging
|What are the dangers and uses of ultraviolet?
|DANGERS: can damage surface cells leading to cancer. Can damage our eyes, leading to cataracts which is a clouding of the lens USES: Fluorescent lamps, detecting forged bank notes, disinfecting water
|What are the dangers and uses of x-rays?
|DANGERS: can be absorbed by the body and can cause mutations in DNA leading to cancer USES: observing the internal structure of objects, medical x-rays
|What are the dangers and uses of gamma rays?
|DANGERS: can be absorbed by the body and can cause mutations in DNA leading to cancer USES: can kill cells so used to sterilize food and kill cancer (radiotherapy). Can also detect cancer
|What are the uses of visible light?
|Vision, photography and illumination
|What are the uses of radio waves?
|Broadcasting, satellite transmissions (can carry TV signals), communications
|How can gamma rays detect cancer?
|Can detect cancer- a radioactive chemical that emits gamma rays is injected into blood, the chemical collects inside cancer cells and a scanner locates the cancer by finding the source of the gamma rays.
|What is a radioactive source?
|Materials that emit ionising radiation all the time
|What is ionising radiation and what are 3 examples?
|Radiation or certain types of high-energy particles that remove electrons from atoms to form ions. Alpha, beta and gamma are types of ionising radiation and all transfer energy from the radioactive material to their surroundings