Waves (electromagnetic, lenses, light and black body radiation) Flashcards

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1
Q

What electromagnetic waves and their features?

A

transverse waves that transfer energy from the source of the waves to an absorber

  • all electromagnetic waves travel at the same velocity (the speed of light) in the air or a vacuum
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2
Q

order the different types of electromagnetic waves from the lowest to the highest frequency?

A

radio, microwaves, infrared, visible, ultraviolet, x-rays, Gamma

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3
Q

How are signals created?

A

radio waves can be produced by oscillations in electrical circuits

when radio waves are absorbed, they cause electrons in the circuit to oscillate

this creates an alternating current with the same frequency as radio waves - this is how the signal is received

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4
Q

what happens when electromagnetic waves are being generated or absorbed?

A

changes in atoms and the nuclear of atoms occur

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5
Q

How can waves be generated?

A

by electrons moving between energy levels, as a result, of heat or electrical excitation can generate waves

i.e. an unstable nucleus can give out excess energy as gamma rays

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6
Q

Why are ultraviolet waves, x-rays and gamma rays harmful?

A

because they transfer a lot of energy

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7
Q

What damages could UV waves cause?

A
  • cause the skin to age prematurely

- increase the risk of skin cancer

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8
Q

What damages can X-rays and gamma rays cause?

A

damage cells by ionising atoms and if absorbed by the nucleus o the cell. can cause gene mutations and cancer

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9
Q

What are the units of radiation dose and what does it measure?

A

sieverts ad is a measure of the risk of harm resulting from an exposure of the body to radiation

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10
Q

What are the uses of radio waves and why?

A
  • television, radio and Bluetooth

this is because radio waves are low energy waves and therefore, not harmful, making them ideal for radio transmissions

are able to be reflected from the ionosphere = allows us to send radio waves very long distances around the Earth

able to travel long distances without being absorbed by buildings or trees

longer wavelength radio waves can also spread out between hills

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11
Q

What are the uses of micro waves and why?

A
  • Satellite communications, cooking food

Microwaves travel in straight lines through the atmosphere, can pass through without being reflected or refracted = good for transmitting signals to satellites in orbit and transmitting them back down to receivers

for heating food, water molecules in food absorb the energy from microwaves, which causes the temperature of the food to increase

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12
Q

What are the uses of infrared waves and why?

A
  • Electrical heaters, cooking food, infrared camera
  • energy of infrared is easily absorbed by the surface of objects
  • electrical heaters etc glow red hot as the electricity flows through them
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13
Q

What are the uses of visible waves and why?

A
  • Fibre optic communications
  • visible light travels down optical fibres from one end to the other without being lost through the sides
  • has a short wavelength, can carry a lot of information ( fire optics used to carry telephone and cable TV signals)
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14
Q

What are the uses of UV waves and why?

A
  • Energy-efficient light bulbs, security marking, sunbeds
  • Ultraviolet has a short wavelength and carries more energy than visible light
  • the energy of the Uv is absorbed by the internal surface of the bulb and is converted into visible light

this requires less energy than a normal light bulb

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15
Q

What are the uses of X-rays waves and why?

A

Medical imaging and treatments

  • X-rays are able to penetrate soft tissue but not bone. A photographic plate behind a person will show shadows where bones are
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16
Q

What are the uses of Gamma waves and why?

A

Medical imaging, tracer, Sterlising food, treatment of tumours,

  • Gamma rays are the most energetic = used to destroy bacteria and tumours
  • gamma emitting source is injected into the patient and its progress is followed around the body. gamma can pass out of the body
17
Q

equation for magnification

A

image height/ object height