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AH Physics > 6.2 Electromagnetic Waves > Flashcards

6.2 Electromagnetic Waves Flashcards

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1
Q

What are electromagnetic waves?

A

Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber without the need of a medium

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2
Q

Why are electromagentic waves different to mechanical waves?

A

Electromagnetic waves do not need a medium to travel through

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3
Q

What do electromagnetic waves form?

A

Electromagnetic waves form a continuous spectrum

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4
Q

Can electromagnetic waves travel through a vacuum?

A

Yes

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5
Q

What happens to the velocity of electromagnetic waves through a vacuum?

A

All electromagnetic waves travel at the same velocity through a vacuum as through air

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6
Q

At what speed to electromagnetic waves travel at?

A

3 x 108 m/s

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7
Q

How are the waves in the electromagentic spectrum grouped?

A

The waves in the electromagnetic spectrum are grouped in terms of their wavelength and their frequency

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8
Q

What does the energy waves transfer depend on?

A

The energy waves transfer depends on the wavelength of the waves

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9
Q

The shorter the wavelength, the ____________ the energy transferred

A

The shorter the wavelength, the higher the energy transferred

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10
Q

What are the types of electromagnetic waves, going from long wavelengths to short wavelengths

A

Going from longwavelengths to short wavelengths:

  1. Radio Waves
  2. Microwaves
  3. Infrared
  4. Visible Light
  5. Ultraviolet
  6. X-ray
  7. Gamma Ray
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11
Q

Which colour has the longest wavelength?

A

Red

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12
Q

Which colour has the shortest wavelength?

A

Violet

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13
Q

Why can humans only detect a limited range of electromagnetic waves?

A

Humans can only detect a limited range of electromagnetic waves as our eyes only detect visible light

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14
Q

Give 2 examples that show the transfer of energy by electromagnetic waves

A
  • Microwave Ovens transfer energy from a microwave source to the food in the oven, which heats it
  • Radiant heaters use infrared radiation to transfer energy from the heater to heat the surroundings
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15
Q

What happens when electromagnetic waves move from one medium to another

A

When electromagnetic waves move from one medium to another, the waves might be:
* Transmitted
* Absorbed
* Reflected
* Refracted

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16
Q

How does refraction occur?

A

Refraction occurs when the speed of the wave changes whilst moving from one substance to another, causing a change of direction

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17
Q

Why does refraction occur?

A

Refraction occurs because waves travel different speeds in different mediums

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18
Q

What are the rules of refraction?

A
  • The light ray changes direction towards the normal when it travels from air to glass
  • The ray changes direction away from the glass when it travels from glass to air
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19
Q

How are radio waves produced?

A
  • Radio waves can be produced by oscillations in electrical circuits
  • This causes the transmitter to produce radio waves with the same frequency of oscillation
20
Q

How are radio waves produced?

A
  • Radio waves can be produced by oscillations in electrical circuits
  • This causes the transmitter to produce radio waves with the same frequency of oscillation
21
Q

How are radio waves absorbed?

What happens?

A

When radio waves are absorbed by a conductor such as an aerial, they induce an alternating current with the same frequency as the radio wave itself, so radio waves themselves can induce oscillations in an electrical circuit

22
Q

Give the 2 ways electromagnetic waves interact with atoms?

A

Electromagnetic waves are either absorbed or generated by atoms

23
Q

What happens when an electromagnetic wave is absorbed by an atom?

A

When an electromagnetic wave is absorbed, it can cause an electron to move to a higher energy level

24
Q

What happens when an electron returns or moves down to a lower energy level?

A

What an electron returns or moves down to a lower energy level, it can generate an electromagnetic wave

25
Q

Where do gamma rays originate from?

A

Gamma rays originate from changes in the nucleus of an atom

26
Q

Which elecromagnetic waves have hazardous effects on the human body?

A
  • Ultraviolet waves
  • X-rays
  • Gamma rays
27
Q

What do the effects of hazardous electromagnetic waves depend on?

A

The effects depend on the type of radiation and the size of the dose

28
Q

What is radiation dose?

A

Radiation dose is a measure of the risk of harm resulting from an exposure of the body to the radiation

29
Q

How is radiation dose measured?

A

Radiation dose in sieverts

30
Q

How many millisieverts in 1 sievert (Sv)

A

1000 millisieverts (mSv) = 1 sievert (Sv)

31
Q

What are the hazardous effects of ultraviolet waves?

A

Ultraviolet waves can cause skin to age prematurely and increase the risk of skin cancer

32
Q

How can humans be protected from ultraviolet waves?

A

Skin creams can be used to block ultraviolet waves and prevent them from reaching your skin

33
Q

What are the hazardous effects of gamma rays and X-rays?

A

X-rays and gamma rays are ionising radiation that can cause the mutation of genes and cancer

34
Q

What are the uses of radio waves?

Why are they suitable for that purpose?

A

Television and Radio
- Because they travel long distances before being absorbed
- They reflect off the ionosphere in the Earth’s atmoshpere so they can be sent across very long distances around the Earth

35
Q

What are the uses of microwaves?

Why are they suitable for that purpose?

A

Satellite Communications and Cooking Food
- They pass through the Earth’s atmoshpere withour reflection or refraction
- They are absorbed by the water molecules in food, which then heat up

36
Q

What are the uses of infrared (waves)?

Why are they suitable for that purpose?

A

Electrical heaters, Cooking food, Infrared cameras
- Easily absorbed by surfaces
- Emitted by hot objects

37
Q

What are the uses of visible light (waves)?

Why are they suitable for that purpose?

A

Fibre optic communications
- Fibre optic cables contain thin strands of glass which reflect visible light inside to carry pulses of light across cables

38
Q

What are the uses of ultraviolet (waves)?

Why are they suitable for that purpose?

A
39
Q

What are the uses of X-rays and gama rays?

Why are they suitable for that purpose?

A

Medical imaging and treatments
- They are highly penetrating

40
Q

What are the differences between each colour in the visible light spectrum?

A

Each colour within the visible light spectrum has its own narrow band of wavelength and frequency

41
Q

What does the colour of an opaque object depend on?

A

The colour of an opaque object is determined by which wavelengths of light are more strongly reflected

42
Q

What happens if all wavelengths are reflected equally in an opqaue object?

A

If all wavelengths are reflected equally, then the object appears white

43
Q

What happens if all wavelengths are absorbed by an opqaue object?

A

If all wavelengths are absorbed the objects appears black

44
Q

How do colour filters work?

A

Colour filters work by absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colour)

45
Q

How would a surface look red in terms of wavelength?

A

When the surface absorbs all the wavelengths except for the red component of the white light, which is reflected off the surface

46
Q

If an object transmits light, what could it be known as?

A
  • transparent
  • translucent

AH Physics (11 decks)

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