Topic 5 - Light And EM Flashcards

1
Q

What is total internal reflection?

A

When light is completely reflected back at a boundary between two mediums
It occurs when light meets a less dense medium at an angle of incidence large than the critical angle.

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2
Q

What is the critical angle?

A

The angle of incidence which causes the angle of reflection to be 90 degrees

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3
Q

What determines the colour of visible light waves?

A

The wavelength and frequency of the light waves.

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4
Q

What colour of visible light has the highest frequency?

A

Violet

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5
Q

What colour of visible light has the largest wavelength?

A

Red

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6
Q

What is meant by the term “specular reflection”?

A

Rays are reflected from a smooth surface in a single direction.

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7
Q

What is meant by the term “diffuse reflection”?

A

Reflection from a rough surface which caused scattering of light rays.

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8
Q

How does a red colour filter work?

A

A red filter absorbs all wavelengths of light other than those in red range spectrum
This means only red light passed through the filter.

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9
Q

What is meant by “opaque”?

A

Not see-through

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10
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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11
Q

What happens to the wavelengths of lights that Aren’t reflected by an opaque object?

A

Wavelengths Absorbed by the object

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12
Q

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

A

White

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13
Q

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

A

Black

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14
Q

What types of waves are EM waves.

A

Transverse

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15
Q

What do EM waves transfer?

A

Energy (not matter)

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16
Q

What type of spectrum do EM waves form?

A

A continous spectrum

17
Q

Order of EM spectrum in terms of increasing wavelength

A
Smallest:
Gamma
X ray
Uv
Visible 
Infrared
Microwaves
Radio
Largest:
18
Q

Highest frequency EM wave:

A

Gamma waves

19
Q

Highest ionising EM wave

A

Gamma waves

20
Q

What properties are all shared by EM waves?

A

All transverse

All travel at the same speed in a vacuum and air (3x10^8 m/s)

21
Q

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

A

Radio waves

22
Q

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

A

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

23
Q

Where do gamma rays originate from?

A

Changes in the nuclei of atoms

24
Q

What health effects can Ultraviolet waves cause?

A

Damage to the surface cells and eyes, leading to skin cancer and eye conditions

25
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.

26
Q

How does electromagnetic radiation affect electron arrangement in atoms?

A

Absorption or emission of electromagnetic radiation can cause electron arrangement to change. (It can excite electrons up or down energy levels or remove electron from atom)

27
Q

What are the effects of body cells absorbing radiation?

A

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

28
Q

State and explain a use of radio waves

A

Communications, because radio waves are long wavelength and can travel Long distance without losing quality

29
Q

State and explain a use of microwaves

A

Cooking, as microwaves are absorbed by and heat water/fat in foods.

30
Q

State and explain uses of infrared radiation

A

Cooking food (as it transfers thermal energy) infrared cameras, short range communication.

31
Q

State and explain used of visible radiation

A

Illuminating (seeing) and fibre Optics as they reflect best in glass (other waves have wavelengths that are too long/short).

32
Q

State and explain used of UV

A

Sterilisation, as it kills bacteria, energy efficient lamps, as it radiates low heat but high energy and sun tanning.

33
Q

State an explain uses of X rays

A

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

34
Q

State and explain used of gamma rays.

A

Gamma rays are used in medical treatments, such as radiotherapy in the treatment of cancer.

35
Q

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

A

Gamma and X rays, as they have the highest energy/highly ionising

36
Q

What is the focal length?

A

Focal length is the distance between lens and focal point.

37
Q

How is the power of lens related to the focal length and the shape of the lens?

A

Power of the lens = inverse of the focal length

Shorter focal length, greater power.
Thicker lens means shorter focal length, so greater the power.

38
Q

What happens in a converging lense? Draw an Example

A

In a converging lens, parallel rays of light are brought to a focus. (Focal point/principal focus)
Also know as convex lense

39
Q

What happens to light in a diverging lense? Draw an example

A

In a diverging lens, parallel rays of light are made to diverge from a point.
Aka concave lens