Waves Flashcards

1
Q

Why would 2 different types of electromagnetic waves be detected at the same time in space?

A

They travel at the same speed

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2
Q

Why do you need monochromatic light in diffraction experiments?

A

Provides consistent wavelength, frequency, and phase so waves produced are coherent. Polychromatic light disperses different wavelengths which travel at different velocities in glass

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3
Q

What diffraction pattern would you get by using a white light source?

A

Central bright fringe with repeating spectrum on either side of the fringe

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4
Q

Define reflection and refraction as well as their similarities and differences

A

Reflection - where a wave changes direction at a boundary between two materials
Refraction - where a wave changes direction as it changes speed when passing from one medium to the other
Similarities - both change direction at boundaries
Differences - reflection only changes direction whereas refraction also changes speed

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5
Q

What happens when a wave slows down or speeds up when entering a new medium and in which conditions will a wave slow down?

A

Slows down - bends towards the normal
Speeds up - bends away from the normal
Waves move slower in denser materials and shallower water

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6
Q

Define coherence

A

(Two) Waves with a constant phase difference which produce stable and periodic interference patterns

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7
Q

Define path difference as well as when maximums and minimums occur

A

Path difference - The difference in distance that a wave travels (from another) to reach a location
Maximum - occurs when the path difference is a multiple of the wavelength/ in phase (n lambda)
Minimum - occurs when the path difference is an odd number of half wavelengths/ in antiphase (n +1/2)

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8
Q

What type of interference happens when a wave is:
1. In phase
2. In antiphase

A

In phase - constructive
In antiphase - destructive

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9
Q

Name the electromagnetic waves and their wavelengths (Longest to shortest wavelength)

A

Radio waves- Around 10^3m to 10^1m
Microwaves - Around 10^-1m to 10^-2m
Infrared - Around 10^-5m
Visible light - 400nm (Red, 4x10^-7m) to 700nm (Violet, 7x10^-7m)
Ultraviolet - Around 10^-8m
X-Rays - Around 10^-10m
Gamma rays - Around 10^-12
REMEMBER - many of the wavelengths overlap each other as EM WAVES ARE CONTINUOUS

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10
Q

Give the definition of a progressive wave

A

A wave that transfers energy (NOT MATTER!!) as a result of oscillations. All points oscillate with the same amplitude. These waves can be either longitudinal or transverse.

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11
Q

What is interference?

A

When two waves meet and superpose at a point which causes a change in overall displacement

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12
Q

What type of waves can be polarised?

A

Transverse waves

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13
Q

Define polarisation

A

When the oscillation of a TRANSVERSE wave is restricted to one plane only
A wave that is restricted to one plane is described to be plane polarised

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14
Q

How do you calculate the refractive index?

A

N = c/v
N = Refractive index - NO UNITS
C = Speed of light in a vacuum - ms^-1
V = Speed of light in a medium - ms^-1

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15
Q

What is the principal of superposition?

A

When two waves meet at a point and superpose, the resultant displacement of the wave at that point is equal to the sum of the displacement of the individual waves

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16
Q

What is the formula used for the Young double slit experiment

A

Lambda = ax/d
Lambda = Wavelength - m
a = Distance between slits - m
x = Distance between two adjacent maxima/minima - m
d = Distance between slits and screen - m

17
Q

What is the formula used for a diffraction grating experiment

A

d x Sin(theta) = n x lambda
d = Distance between slits - m
Sin(theta) = Angle between 0th and “nth” maxima - Degrees
n = Order of maxima - NO UNITS
Lambda = Wavelength - m

18
Q

Define intensity in terms of waves as well as the equations and units

A

Radiant power through a surface with unit area
I=P/A I=P/4pi x r^2
Base units - kgs^-3
P= power
A= area