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physics > Electomagntic Spectrum and Light > Flashcards

Electomagntic Spectrum and Light Flashcards

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1
Q

What is total internal reflection

A

When light is completely reflected back at a boundary between two mediums

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2
Q

When does total internal reflection occur

A

When light meets a less dense medium at an angle of incidence larger than the critical angle

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3
Q

What is the critical angle

A

The angle of incidence which caused the angle of reflection to be 90°

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4
Q

What determines the colour of visible light waves

A

Wavelength and frequency of the light waves

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5
Q

What colour of visible light has the highest frequency

A

Blue

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6
Q

What colour of visible light has the largest wavelength

A

Red

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7
Q

What is meant by term ‘specular reflection’

A

Rays are reflected from a smooth surface in a single direction

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8
Q

What is meant by ‘diffuse reflection’

A

Reflection from a rough surface which causes scattering

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9
Q

How does 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

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10
Q

opaque

A

Not see through

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11
Q

What governs 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

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12
Q

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

A

They are absorbed by the object

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13
Q

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

A

White

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14
Q

What colour does an object appear if all wavelengths are absorbed

A

Black

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15
Q

What types of waves are electromagnetic waves

A

Transverse

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16
Q

What does electromagnetic waves transfer

A

Energy (NOT matter)

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17
Q

What type of spectrum do electromagnetic waves form

A

A continuous spectrum

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18
Q

Order of electromagnetic spectrum in order of INCREASING WAVELENGTH

A

Gamma (shortest wavelength)
X-ray
Ultraviolet
Visible
Infrared
Microwave
Radio (longest wavelength)

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19
Q

What is highest frequency of electromagnetic wave

A

Gamma waves

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20
Q

Highest energy electromagnetic wave

A

Gamma waves

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21
Q

What properties are shared by all of the electromagnetic waves

A

All transverse
All travel at the same speed - 3x10^8 m/s
Can travel through a vacuum

22
Q

What range of frequencies of electromagnetic waves can be detected by the human eye

A

400-700 nanometres

23
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 vacuum and air

24
Q

What can happen when radiation strikes an object

A

It can be…
Transmitted
Reflected
Absorbed

25
Q

What do all bodies (objects) emit and absorb

A

Infrared radiation

26
Q

What happens to the quantity of infrared radiation emitted by an object as temperature increases

A

The hotter the object the more infrared radiation it will emit

27
Q

What happens to the rule of radiation emitted by an object as temperature increases

A

Hotter the body the shorter the wavelength of radiation released

28
Q

What is required for a human body to be at a constant temperature

A

Body would need to emit radiation at the same rate that it absorbs it.
It needs to radiate at the same average power that it absorbs

29
Q

Intensity and wavelength distribution of any emission depends on what

A

Temperature

30
Q

What is meant by intensity

A

The power transferred per unit area
It is a measure of the energy transferred by a wave

31
Q

What will happen if the average power that an object radiates is less than it absorbs

A

The temperature of the object will decrease

32
Q

What can be said about the rates of emission and absorption for a body increasing in temperatures

A

The body is absorbing radiation faster than it is emitting it

33
Q

Two factors that affect the temperature of the earth

A
  1. Earths rate of absorption and emission of radiation
  2. The amount of reflection of radiation into space
34
Q

How does the earths atmosphere affect radiation

A

The atmosphere largely absorbs or reflects radiation from the sun, preventing it from reaching the earth. Some radiation, however, is allowed to pass through and warms the earth

35
Q

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

A

Radio waves

36
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 frequency as the waves themselves

37
Q

Where do gamma rays originate from

A

From changed in the nuclei of atoms

38
Q

What health effects can ultraviolet waves cause

A

Cause the skin to age prematurely
Increase risk of developing skin cancer

39
Q

What health effects can x-rays and gamma rays cause

A

Ionising radiation so can cause mutations in genes
Can lead to increased risk of developing various cancers

40
Q

What health effects can infrared rays cause

A

Cause burns to skin or tissue

41
Q

How does EM radiation affect the electron arrangement in atoms

A

Absorption or emission of electromagnetic radiation can cause electron arrangement to change. It can remove electrons from the atom or move electrons further from the nucleus

42
Q

How do atoms become ions

A

Losing outer electron

43
Q

What are the effects of body cells absorbing radiation

A

Large amounts damage cells
Smaller amounts cause mutation, causing cells to divide which can lead to cancer

44
Q

Stage and explain use of radio waves

A

Communications
Because radio waves are long wavelength and can travel long distances without losing quality

45
Q

State an explain use of microwaves

A

Cooking
As microwaves are absorbed by heat fat/water in foods

46
Q

State and explain use of infrared radiation

A

Cooking food
As it transfers thermal energy

47
Q

State and explain use of visible radiation

A

Fibre optics
As they reflect best in glass

48
Q

State and explain uses of UV radiation

A

Sterilisation
As it kills bacteria

49
Q

State and explain uses of X-rays

A

Medical imaging and treatment
Because they are very high energy and can easily penetrate body tissues

50
Q

State and explain use of gamma rays

A

Medical treatments
Such as radiotherapy in the treatment of cancer

51
Q

Which waves of the EM spectrum are regarded as the most dangerous

A

Gamma and X-rays as they have highest energy

physics (5 decks)

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