# Intoduction to waves

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What is a wave?
It is a disturbance that transfers energy from one place to another.
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State what is meant by the amplitude of a wave.
This is the maximum disturbance of a wave from the original position (rest position).
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State what is meant by the wavelength.
It is the distance between two similar points on a wave.
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State what is meant by the frequency of a wave.
This is the number of cycles of a wave per second.
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State what is meant by displacement.
The distance a wave moves a particle from its original position (rest position)
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State what is meant by the time period of a wave.
The time between two similar events.
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State what is meant by the period of a wave.
Points on a wave, which are a whole number of wavelengths apart.
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State what is meant by the wave velocity.
The speed of a wave.
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State what is meant by transverse waves.
Vibrations that are at right angles to the direction of travel (e.g light and other electromagnetic radiation).
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State what is meant by longitudinal waves.
Vibrations that are along the same direction as the direction of travel (e.g sound waves and P waves - seismic waves that travel through solids and liquids).
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State what is meant by polarised waves.
This is where the displacement is travelling in one of the possible transverse directions. Polarisation occurs when light travels through a polarising filter (polaroid filter) It only allows light waves if they are vibrating in the correct plane.
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By the alternating (repeating) current in radio aerials.
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What are radio waves used for?
They are used for communication, such as, television, phones and radios.
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State a few properties of radio waves.
It's absorbed by metals, it is unable to deeply penetrate into certain materials, for instance, rocks, they have lower frequencies & longer wavelengths.
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What danger is associated with radio waves?
Radio waves carry a low risk however, large doses of radio waves may cause cancer, leukemia and other disorders.
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Using an antenna or an electronic to identify the electric circuit.
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How are microwaves produced?
By alternating current in the special electronic devices.
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How are microwaves used?
It is mainly used by microwave ovens. Mobile phones also use microwave radiation for communication.
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State a few properties of microwaves.
It penetrates through glass easily, it is absorbed by water, fat and metals.
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What danger is associated with microwaves?
Low level of risk as they have a low frequency thus they carry small amount of energy. Bones from skull can absorb this radiation when you make a call.
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How are microwaves detected?
It is detected by special electronic devices or antennas.
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It is produced by warm and cold objects e.g our bodies and our surroundings.
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What is infrared radiation used for?
It is used in heater and night vision equipment. Infrared radiation can be detected at night. It is also used by television remote controls, security lights, burglar alarms.
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State a few properties of infrared radiation.
It's strongly absorbed by glass and water, particles are less scattered compared with visible light, it's absorbed by water vapour, carbon dioxide and ozone.
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What danger is involved with infrared radiation?
It involves a low level of risk, infrared radiation is felt as heat - can cause skin burns, especially under the eyes.
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Photography (that includes infrared sensors), heating effect e.g radiometer and photoconductive cells.
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How is visible light produced?
It is produced by hot objects e.g on a furnace.
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What are the uses of visible light?
Visible light is used by our eyes to view our surroundings, plants use light as an energy source for photosynthesis and photographic images require visible light.
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State a few properties of visible light.
Causes chemical reactions, light is unable to penetrate through most solids, it can penetrate through glass and water.
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What are the dangers associated with visible light?
Visible light is mainly safe and harmless, too much light can damage the retina in our eyes and cause blindness and high powered lasers damages the skin by causing burns.
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How is visible light detected?
Visible light is detected by our eyes, photography and photocell
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How is ultraviolet produced?
It is produced by very hot objects e.g the Sun.
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What are the uses of ultraviolet light?
It is used in sunbeds, security pens, fluorescent lights, detecting forged bank notes, to kill microbes in hospitals, to sterilise surgical equipment and it’s used to treat vitamin D deficiency
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What are the properties of ultraviolet light?
It's absorbed by glass and by ozone, it passes through quartz and to some extent water, involved in chemical reactions e.g sun tan and it ionises atoms.
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What dangers are associated with ultraviolet light?
Large doses of UV can damage the retina in your eyes, too much exposure to UV can cause sunburn and skin cancer (in more serious cases).
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How is ultraviolet light detected?
Photography, photoelectric cells and fluorescence.
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How are X-rays produced?
It is produced when the electrons have reduced their speed and their energy has been converted into X-rays.
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What are X-rays used for?
They are used to examine bones, fractures, joints, condition, teeth.
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State a few properties of X-rays.
They cause ionisation, they can mutate DNA therefore, increasing the likelihood of cancer, it affects the developing fetus if it is exposed to the x rays, bones and metal absorb the x rays as opposed to soft tissues and they affect photographic film.
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What dangers are associated with X-rays.
Risk of mutating DNA thus increasing the likelihood of developing cancer, the fetus would be affected if it is exposed to the X-rays, X-rays can kill living cells.
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How are X-rays detected?
Photography, special devices and phosphorescence.
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How are gamma rays produced?
It is produced by nuclear decay in the nucleus of atoms.
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What are the uses of gamma rays.
They are used to kill cancerous cells, to sterilise surgical equipment, to sterilise harmful bacteria in food.
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What are the properties of gamma rays?
They cause ionisation, they can mutate DNA therefore, increasing the likelihood of cancer, can be hazardous, they able to penetrate objects, has no electric charge or mass, they have higher frequencies and shorter wavelengths.
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What are the dangers of gamma rays?
Risk of mutating DNA thus increasing the likelihood of developing cancer, the fetus would be affected if it is exposed to the rays, they can kill living cells.
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How are gamma rays detected?
Photography, special devices and phosphorescence.
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## Other cards in this set

### Card 2

#### Front

State what is meant by the amplitude of a wave.

#### Back

This is the maximum disturbance of a wave from the original position (rest position).

### Card 3

#### Front

State what is meant by the wavelength.

### Card 4

#### Front

State what is meant by the frequency of a wave.

### Card 5

#### Front

State what is meant by displacement.