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Physics > Waves > Flashcards

Waves Flashcards

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1
Q

Definition of a progressive wave

A

A wave that carries energy from one place to another without transferring any material

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2
Q

What do these waves do: EM/X-ray & Gamma

A

EM - Heat
X-ray & Gamma - Ionisation

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3
Q

What is a transverse wave (Give an example)

A

A wave that vibrates perpendicular to direction of travel/energy transfer (EM)

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4
Q

What is a longitudinal wave (Give an example)

A

A wave that vibrates along the direction of energy transfer (Sound)

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5
Q

What is a polariser

A

A filter that only transmits waves in a singular plane

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6
Q

Define superposition

A

When two or more waves pass through each other

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7
Q

What does constructive/destructive interference do?

A

Constructive - Bigger amplitudes
Destructive - No amplitude

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8
Q

Define coherent

A

Two sources which have the same frequency & wavelength

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9
Q

Define monochromatic

A

Light with a single wavelength

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10
Q

What type of path difference does constructive/destructive

A

Constructive - path difference wavelength
Destructive - path difference 1/2 wavelength

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11
Q

Define a stationary wave

A

Two progressive waves superpose with the same frequency & wavelength moving in opposite directions

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12
Q

What is intensity, what is meant by intensity of light and what is the equation for it. Intensity for monochromatic light changes, why?

A

Intensity - Power per unit area
Intensity of light - Number of photons
Power per unit area
Changes because even though all photons are the same, there are more photons per second

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13
Q

Explain diffraction pattern of white light

A

Bright central fringe
Fringes decrease in intensity
Blue (inside) to red (outside) colour spectrum

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14
Q

Difference between red and blue light

A

Red - Longer wavelength
Blue - Shorter wavelength

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15
Q

How does Youngs Double Slit experiment work and explain the outcome

A

Slits same size as wavelength
Two Diffractions
Fringes made of a bright point and decrease in intensity when moving to outside.

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16
Q

Who were the people in different light theories and what were their theories

A

Newton - Corpuscles (particles)
Huygen - Waves

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17
Q

Equation to find slit seperation

A

Area (m^3) divided b y number of slits

18
Q

What happens when light is shone through more slits

A

Interference patterns are sharper

19
Q

What is the EM spectrum, how is it classed.

A

Radio Micro Infa-red Visible Ultra Violet X-ray Gamma
Longer wavelength/Less energy ——————–> Lower wavelength/More energy

20
Q

Examples of what EM waves are used for

A

R - broadcasting M - Radar I - Radiators V - Light UV - Florescent lights X-ray - Inside viewing G - Medicine (Cancer)

21
Q

Different wavelengths for EM spectrum

A

R - 10^3
M - 10^-2
I - 10^-5
V - 10^-6
UV - 10^-8
X - 10^-10
G - 10^-12

22
Q

Different frequencies for EM spectrum

A

R - 10^4
M - 10^8
I - 10^12
V - 10^15
UV - 10^16
X - 10^18
G - 10^20

23
Q

Visible light spectrum and the wavelengths of their colours

A

Red -> Purple Longer -> Shorter wavelength
R(740-625)
O(625-590)
Y(590–565)
G(565-520)
LB(520-500)
B(500-435)
P(435-380) nano meters

24
Q

Describe the Balmer series

A

Hydrogen spectrum
P(n6-n2)
G(n5-n2)
LB(n4-n2)
R(n3-n2)

25
Q

Definition of a refractive index

A

How much light slows down in a material

26
Q

What happens to wave in refraction

A

Speed and wavelength change, frequency remains constant

27
Q

What is needed for light to refract towards normal

A

Refractive index of material 1 is smaller than material 2

28
Q

What is needed for light to refract away from the normal

A

Refractive index of material 1 is bigger than material 2 and angle of incidence is less than the critical angle

29
Q

What is needed for total internal reflection

A

Refractive index of material 1 is bigger than material 2 and angle of incidence is bigger than critical angle.

30
Q

How does a light ray travels along a boundary

A

Refractive index of material 1 is bigger than material 2 and angle of incidence is equal to the critical angle.

31
Q

What is an optical fibre

A

A thin flexible tube of glass or plastic fibre that carries signals at light at a fast speed

32
Q

What does absorption do to waves

A

The energy is lost through the material resulting in a reduced amplitude

33
Q

What are pros and cons of optical fibres

A

Pros - No signal degradation over distance/Fast/Can travel very long distances
Cons - Expensive/Hard to replace

34
Q

What does the cladding of a fibre do

A

Protects the core for damage

35
Q

How does a fibre work

A

Since the refractive index of the core is bigger than the cladding, it allows TIR since the fibre is so small the rays always hit the boundary at an angle bigger than the critical angle.

36
Q

Define modal dispersion

A

Light rays take different paths and arrive at the end at different times making there signal smeared.

37
Q

How can we stop modal dispersion

A

Use a single mode fibre where light can only take one path

38
Q

Define material dispersion

A

Light has different wavelengths and speeds causing light to arrive at different times.

39
Q

How can we stop material dispersion

A

Use monochromatic light

40
Q

What is pulse broadening

A

When dispersion occurs, signals can overlap and become muddled

41
Q

How do we reduce pulse broadening

A

Use an optical fibre repeater which boosts and regenerates the signal

42
Q

What is the musical name for harmonics

A

Octaves

Physics (12 decks)

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