Waves And The EM Spectrum Flashcards

1
Q

What happens towards the gamma rays end of spectrum

A
  • more energy transferred
  • short wavelength
  • high frequency
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2
Q

What are the same for all electromagnetic waves

A
  • are all transverse
  • travel at the speed of light in a vacuum (3x10^8 m/s)
  • travel at the same speed through the same material
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3
Q

How did Herschel make observations of the sun

A

Put a coloured filter over a telescope to try and make it safer

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4
Q

What did Herschel notice

A

Different coloured filters heat up by different amounts

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5
Q

What did Herschel do when he observed different coloured filters heat by different amounts, and what did he observe

A

He put a thermometer in the different colours by using a prism to break up the visible light. The temperature rose as as he moved from violet to red. He measured the temperature where there was no visible light at the red end of the spectrum

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6
Q

What did Herschel discover

A

Discovered that the temperature was highest at the red end of the spectrum. He discovered infrared (beyond red)

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7
Q

What did Ritter discover

A

He discovered ultraviolet when he tried to find invisible rays at the violet end of the spectrum

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8
Q

What did Ritter use and what did he see

A

He used silver chloride; which turns black when exposed to light. Happened fastest when exposed to invisible rays at the violet end

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9
Q

What is there towards the radio waves end of the spectrum

A
  • less energy transferred
  • long wavelength
  • low frequency
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10
Q

What gives a tan but can cause cancer in cells

A

Ultraviolet

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11
Q

What is used to sterilise surgical instruments

A

Gamma rays

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12
Q

What is used to make toast

A

Infrared

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13
Q

What is used to change channels in a remote

A

Infrared

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14
Q

What is used to send information to and from satellites

A

Microwaves

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15
Q

How do microwaves heat food

A

The water molecules in the food absorb the microwave radiation and gain heat energy

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16
Q

What is reflection

A

The change in direction of a wave, at a boundary between materials, which does not enter the new material

17
Q

What is the normal

A

A line perpendicular (at 90°) to the surface

18
Q

What is the law of reflection

A

The angle of incidence is always equal to the angle of reflection

19
Q

When a ray passes from air to glass

A

It slows down, as the refractive index of air is 1 and the refractive index of glass is 1.5

20
Q

When Ray passes from glass to air

A

It speeds up, as it is going from a higher index to a lower

21
Q

For entering a material with a higher refractive index

A

It refracts towards the normal

22
Q

For entering a material with a lower refractive index

A

It refracts away from the normal

23
Q

Diamond has a refractive index of 2.4 and water 1.3 what does this mean

A

The refractive index is a ratio that shows how much the material slows down the light. This shows that light travels faster in water than diamond

24
Q

What is total internal reflection

A

It occurs when a wave no longer passes through the surface of a material it is inside. Instead, it is reflected

25
Q

What is the critical angle

A

The certain angle that light is shone at for total internal reflection to occur

26
Q

If an angle of incidence is less than the critical angle

A

It will result in refraction

27
Q

If an angle of incidence is equal to the critical angle

A

No light leaves the material

28
Q

If an angle of incidence is greater than the critical angle

A

It will result in reflection

29
Q

What is fibre optic

A

Fibre optic cables use total internal reflection. Light and infrared radiation carries information down thin, solid plastic fibres

30
Q

What is an endoscope

A

An endoscope is an instrument used medically. It has a bundle of very thin optical fibres which are used with lenses to see insides

31
Q

How does the endoscope work

A
  • the endoscope is put into the person
  • light enters via the fibre optic cables
  • it gets there by TIR
  • the light is reflected off the person’s insides
  • it returns by TIR
  • a computer uses the reflected light to produce an image
32
Q

When the waves go from deep water to shallow water

A

Wavelength decreases

33
Q

Explain what happens to the direction of travel of waves when they go from deep water to shallow water

A

Due to refraction, the waves change direction and decrease in speed

34
Q

What are the differences between longitudinal and transverse waves

A

Transverse waves are light waves. They are perpendicular to energy transfer. Longitudinal waves are sound waves and move upwards and downwards

35
Q

What does a frequency of X Hz mean?

A

There are X numbers of cycles per second

36
Q

Why are ultraviolet less harmful than xrays

A

They are both ionising, but xrays are more ionising.