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LC Physics > Light as a wave > Flashcards

Light as a wave Flashcards

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1
Q

What is n in relation to monochromatic light

A

the order of the beam

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2
Q

What is d in relation to monochromatic light

A

distance between gratings on diffraction grating. Must be in metres

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3
Q

What is angle for formulae in relation to monochromatic light

A

Theta is the angle from the zeroth order to the point you are looking at on the screen

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4
Q

How can you find the measure of the angle for the experiment of monochromatic light

A

use tan of angle = opposite over adjacent

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5
Q

In the experiment to estimate the wavelength of monochromatic light what would happen to the position of the images if wavelength of light was decreased

A

They would get closer

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6
Q

In the experiment to estimate the wavelength of monochromatic light what would happen to the position of the images if there were less lines on the refraction grating

A

They would get closer

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7
Q

What is a spectrometer

A

An optical instrument used to examine spectra and to measure the wavelength of light

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8
Q

Explain the parts of the spectrometer

A

Turntable,
The vernier Scale
Slit- needs to be as narrow as possible so accurate image is found
Collimator- Convex lens at one end and narrower tube has slit
Telescope- Free to rotate. Has cross wires t enable exact image position to be determined

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9
Q

Give the steps in using the spectrometer

A
  1. move eyepiece until cross threads are in focus
  2. Focus on distant object moving cross theads and eyepiece to focus
  3. Illuminate slit and look through telescope
  4. Move slit relative to collimator so it’s in focus
  5. Adjust width of slit
  6. Level table
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10
Q

Explain diffraction

A

Spreading of a wavefront into the geometrical shadow when it passes through a gap or around an obstacle

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11
Q

What type of wave is light

A

electromagnetic wave

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12
Q

How do you make diffraction more noticeable

A

If gap or obstacle is approximately equal to or less than the wavelength of the wave

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13
Q

What is the grating constant of a diffraction grating

A

The distance between two adjacent slits on the grating

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14
Q

Explain monochromatic light and give two sources

A

Not a of different wavelengths (ie. Cannot be broken into a number of colours) ex: Laser, Sodium vapour lamp

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15
Q

Describe what happens to monochromatic light that falls on a diffraction grating

A

Light passes through slits in diffraction grating and diffraction occurs.
The diffracted waves overlap and interference occurs
Destructive interference occurs- no light visible
Constructive interference occurs- light visible
Light that passes straight through grating is the zero order image

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16
Q

What is the formula for diffraction grating

A

n(lamda) = dsin(Angle)

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17
Q

What is the formula for the maximum order image

A

n(lamda) = dsin(90)

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18
Q

Explain polarisation

A

The process of confining the vibrations of the light wave to one direction

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19
Q

What happens if light passes through a substance called polaroid

A

It becomes plane polarised.
Polaroid absorbs the light vibrating at right angles to it’s axis and only allows light that is vibrating parallel to it’s axis pass through.

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20
Q

Explain stress polarisation

A

Two pieces of polaroid held at right angles so no light passes through- polarised
Light can pass through if perspex is placed in between as direction of light vibration changes
When viewed from right hand side different colours of light are observed.
Colour pattern changes if perspex is under strain

21
Q

Explain dispersion and name two methods

A

The separating out of wavelengths (colours) present in light is called dispersion

22
Q

Describe light that is dispersed by a prisim

A

Red light bends the least and violet bends the most. It results in one spectrum

23
Q

Describe light that is dispersed by grating

A

Red light bends mos, violet bends least and spectrum is formed for each value of n other than n=0. No dispersion for zero order image

24
Q

How does a rainbow occur

A

Dispersion is responsive. For rainbow to occur sunlight and moisture in air is needed (h20)

25
Q

What is recombination

A

A second prisim will recombine the constituents of white light to again form white light

26
Q

What are the primary colours of light

A

Three colours that combine to give white light- red, green, blue

27
Q

What are the secondary colours of light

A

Obtained by combining any two primary colours
Yellow = red and green
Cyan= blue and green
Magenta- red and blue

28
Q

What are complementary colours of light

A

A primary and secondary colour that combine to give white light are complementary colours
Blue + yellow
Red + Cyan
Green + Magenta

29
Q

Describe the speed and type of waves that electromagnetic waves are

A

In a vacuum they travel at 3x10^8

They are all transverse waves and can be polarised

30
Q

Name the types of electromagnetic radiation on the electromagnetic spectrum from smallest wavelength to biggest

A 
Gamma ray
X-ray
UV
Visible Light
Infrared
Microwaves
TV and radio waves
31
Q

What is the approx wavelength of gamma ray

A

0.01nm

32
Q

What is the approx wavelength of X-ray

A

1nm

33
Q

What is the approx wavelength of UV

A

0.1μm

34
Q

What is the approx wavelength of Visible light

A

0.4μm-0.7μm

35
Q

What is the approx wavelength of Infrared

A

0.01mm

36
Q

What is the approx wavelength of Microwaves

A

1cm

37
Q

What is the approx wavelength of Tv and Radio waves

A

1km

38
Q

Explain line spectrum in terms of light production

A

source of light is luminous gases and vapours at low pressure ex: sodium vapour

39
Q

Explain band spectrum in terms of light production

A

sources is molecules of glowig gases or vapours ex: oxygen or nitrogen gas

40
Q

Explain continuous spectra in terms of light production

A

Could consist of all the colours in white light. The source is an incandescent solid or liquid eg: tungsten filament lamp

41
Q

Explain incandescent

A

White hot

42
Q

What can produce UV light in life and in lab

A

A white hot solid can produce UV light - Sun

In the lab ordinary filament lamp emits a small amount or usually a mercury vapour lamp is used

43
Q

How it UV light detected

A

Effect on a photographic plate or by Fluorescence- absorbs UV light and emits it as visible light

44
Q

What are the properties of UV light

A

Causes certain substances to fluoresce- vaseline
Effects photographic plate more than visible light
Causes sunburn
Produces vitamin D in skin
Does not pass through ordinary glass only quartz glass
High frequency so it emits electrons from metal surfaces (photoelectric effect)

45
Q

What emits IR radiation?

A

All hot objects emits IR radiation ex: human body or exhaust pipe of car. As temperature increases objects emits more IR radiation of shorter wavelength

46
Q

How is IR radiation detected

A

Using thermometer with blackened bulb

47
Q

What are the properties of IR radiation

A

Effects photographic plate- can take photo in dark
Thermogram
Passes through fog and mist- photographs
Causes substances on which it falls to heat up

48
Q

Explain Greenhouse effect

A

Some radiation penetrates atmosphere and is absorbed by earth then re emitted
Wavelength of re-emitted is longer and cannot pass through atmosphere so it keep planet warm
Gas CO2 traps this radiation
Since CO2 levels are rising with burning of fossil fuels temperature of earth is rising.

LC Physics (9 decks)

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