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34 Cards in this Set
- Front
- Back
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What is an electromagnetic wave? |
Electric and magnetic disturbances that can be used to transfer energy from a source to an absorber. |
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What is the electromagnetic spectrum |
Radio waves, microwaves, infrared, visible light, ultraviolet radiation, x-rays, gamma radiation |
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What is the equation for wave speed? |
Wave speed (m/s) = frequency (Hz) * wavelength (m) |
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What’s the pattern in the electromagnetic spectrum? |
As the wavelength decreases from radio waves to gamma rays, the energy and frequency increase. |
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What is white light? |
Light that contains all the colours of the visible spectrum in it. |
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What is the visible spectrum?what |
Red, orange, yellow, green, blue, indigo and violet. The wavelength decreases along this spectrum. |
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What is infrared radiation?j |
All objects emit infrared radiation. The hotter the object is the more infrared radiation it emits. Infra radiation is absorbed by the skin it can damage, burn, or kill your skin cells because it heats up the cells. |
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What is infrared used for? |
- optical fibres because it’s absorbed less than usable light in the glass fibres - tv remotes, send out infrared signals to tv. Used because they can be easily produced and read electronically. - infrared cameras - heating equipment |
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What are microwaves used for? |
- Communications such as satellite TV and mobile phones, because they can pass through the atmosphere and reach satellites in space. - microwave ovens because they can penetrate food and are absorbed by water molecules heating the food up. |
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What are radio waves used for? |
- Carry radio, tv and mobile signals - Bluetooth |
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What are the harms of microwaves and radio waves? |
They can penetrate peoples bodies and heat up internal parts. |
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What is a carrier wave? |
A wave that carries any type of signal, could be radio waves, microwaves, infrared radiation or visible light. The type of wave used depends on how much information is in the signal and the distance the signal has to travel. |
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What do shorter wave lengths do compared to longer ones? |
- they can carry more information - they have a shorter range - they spread out less |
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Why are microwaves used for satellite communications? |
Shorter wavelength so they don’t spread out that much meaning they can reach space without weakening the signal. |
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Why are short radio waves used for tv broadcasting? |
They’re able to carry more information compared to longer ones. |
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Why are radio waves used for radios and emergency services? |
They’re range is shorter meaning the waves are limited to the area around the transmitter which is ideal for radios and emergency services. |
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What are the dangers of mobile phones? |
They emit radio waves and some scientists think the radiation mace affect the brain. |
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How do radio stations transmit signals? |
Back (Definition) |
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What are optical fibres? |
Very thin glass fibres which are used to transmit signals carried by light or infrared radiation. |
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Why are optical fibres better than radio waves or microwaves? |
- carry more informational because they have shorter wavelengths/frequencies and so can carry more pulses of waves - more secure because the signals stay put in the fibre |
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How are ultraviolet waves used in inks that glow in ultraviolet light? |
The ink absorbs some of the ultraviolet light causing some of the chemicals in the substance to emit visible light causing us to see it. |
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How are ultraviolet waves harmful? |
- can blind people because wavelength are smaller meaning they carry for energy. - harmful to skin, can cause sunburn and skin cancer. Can also age skin prematurely. |
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How are x-rays and gamma rays similar? |
- both travel through substances that aren’t too thick - short wavelength - carry more energy |
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How are x-rays produced? |
They’re produced when electrons or other particles moving at high speeds are stopped. |
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How are gamma rays produced? |
They’re produced by radioactive substances when unstable nuclei release energy. |
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What are x-rays used for? |
- used to detect cracks in metal objects. This is possible because the denser the object is, the more x-rays it absorbs meaning it creates an image. - similarly used for human x-rays |
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How are gamma rays used? |
- kills harmful bacteria such as sanitising food and medical equipment. - kills cancer cells, a narrow beam of gamma rays is directed at the tumour to kill the tumour cells. |
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What is ionisation and how do x-rays and gamma rays do this? |
X-rays and gamma rays pass through substances which can knock electrons out of atoms. The atoms then become charged because they loose electrons, this is ionisation. |
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Why is ionisation harmful? |
It can damage or kill the cell which is why x-rays and gamma rays are dangerous as they can cause cancer. A low dose of the rays can cause gene mutation and cancerous growth. |
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How do x-ray photographs work? |
1) x-rays pass through patients soft tissue but are absorbed by bones and teeth. The parts of the film that the x-rays reach become dark. 2) lead plates between X-ray tube and patient stop the rays reaching other parts of the body as the plate has a small hole to direct the rays. Lead is a good absorber of x-rays. 3) a flat-panel detector contains a charged couple device. The CCS conveys the X-rays into light. The light creates electronic signals that are sent to a computer which displays a digital x-ray image. |
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How do x-ray’s work on soft tissue? |
Soft tissue can be filled with a contrast medium that absorbs x-rays easily. This enables the organ to be seen on the radiograph. |
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What is radiation dose and what does it depend on? |
Radiation dose received by a person is the measure of the damage done to their body by ionising radiation. It depends on: - type of radiation - how long the body is exposed to it - energy/second absorbed by body |
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What is X-ray therapy? |
Destroys cancerous cells. A plate is used to direct the rays to the cancerous cells without harming the healthy cells around it. |
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Why are the wavelengths shorter in X-ray therapy than for x-ray photography? |
Shorter wavelengths carry more energy therefore they can kill cancerous cells. Image x-rays are not high enough to kill cancer cells but can pass through soft tissue and get absorbed by bones which is perfect for a radiograph. |
