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Physics > Electromagnetic Waves > Flashcards

Electromagnetic Waves Flashcards

Topic 6 - Waves

1
Q

What type of spectrum do electromagnetic waves form?

A

A continuous spectrum

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2
Q

Order the types of electromagnetic radiation from lowest to highest frequency

A
  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
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3
Q

How do the speeds of EM radiation differ in a vacuum and in air?

A

Electromagnetic waves all travel at the same speed in a vacuum and in air

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4
Q

What property of waves in different mediums causes refraction?

A
  • Velocity
  • Wave speed is slower in denser materials, causing refraction
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5
Q

In which direction (relative to the normal) do waves refract when entering a denser medium?

A
  • They bend towards the normal
  • The angle of refraction is less than the angle of incidence
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6
Q

What type of waves can be produced by oscillations in an electrical circuit?

A

Radio waves

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7
Q

How can radio waves create an alternating current in a circuit?

A

When radio waves are absorbed, they can induce oscillations in a circuit with the same frequecy as the waves themselves

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8
Q

Where do gamma rays originate from?

A

They originate from changes in the nuclei of atoms

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9
Q

What health effects can X-rays and gamma rays cause?

A
  • They are ionising radiation so can cause mutations in genes
  • They can lead to increased risk of developing various cancers
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10
Q

What health effects can ultraviolet waves cause?

A
  • They can cause the skin to age prematurely
  • They can increase the risk of developing skin cancer
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11
Q

Give three practical uses for infrared radiation

A
  1. Electrical heaters
  2. Cooking food
  3. Infrared cameras
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12
Q

Give two practical uses for microwave radiation

A

1.Satellite communications
2. Cooking food

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13
Q

Give two practical uses for radio waves

A
  1. Television transmission
  2. Radio transmission
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14
Q

What wave phenomenom is used by lenses to form an image?

A

Refraction

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15
Q

How does a convex lens form an image?

A

Parallel rays of light are refracted and brought together at a point known as the principal focus

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16
Q

What is meant by the focal length of a lens?

A

The distance from the lens to the principal focus

17
Q

What is the difference between the image produced by a convex and a concave lens?

A
  • Convex lenses can produce real or virtual images
  • Concave lenses can only produce virtual images
18
Q

Why does magnification not have a unit?

A
  • It is the ratio between image height and object height
  • Ratios do not require units
19
Q

What symbol is used to represent a convex lens in a ray diagram?

A

/|\
|
|
|/

20
Q

What symbol is used to represent a concave lens in a ray diagram?

A

\/
|
|
/\

21
Q

What determines the colour of visible light waves?

A

The wavelength and frequency of the light waves

22
Q

What colour of visible light has the highest frequency?

A

Blue

23
Q

What colour of visible light has the largest wavelength?

A

Red

24
Q

What is meant by the term ‘specular reflection’?

A

Reflection from a smooth surface in a single direction

25
Q

What is meant by the term ‘diffuse reflection’?

A

Reflection from a rough surface which causes scattering

26
Q

How does a red colour filter work?

A
  • A red filter absorbs all wavelengths of light other than those in the red range of the spectrum
  • This means only red light passes through the filter
27
Q

What determines the colour of an opaque object?

A
  • Different objects reflect different wavelengths of light by different amounts
  • The wavelengths that are most strongly reflected determine the colour
28
Q

What happens to the wavelengths of light that aren’t reflected by an opaque object?

A

Any waelengths that aren’t reflected are absorbed by the object

29
Q

What colour does an object appear if all wavelengths are reflected by equal amounts?

A

White

30
Q

What colour does an object appear if all wavelengths are absorbed?

A

Black

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