Physics
Define 'wavelength'
The smallest distance between two points with the same oscillation pattern
Define 'frequency'
The number of oscillations per unit of time
Define 'Period'
The time taken for once complete oscillation to occur
Define 'Displacement'
The distance any part of the wave has moved from rest position (can be positive/negative)
Define 'amplitude'
The maximum displacement from rest position to peak (IT'S ALWAYS POSITIVE)
What is common about all EM waves?
They all travel at the same speed
Give the formula for light intensity
Light intensity(Wm^-2) = Power(W) / Surface Area(m^2)
What 2 things are intensity directly proportional to?
- (Amplitude)^2
- (1 / (distance^2))
Define 'Reflection'
Where a wave bounces back after hitting a boundary
Finish the sentence, "Angle of incidence equals..."
Angle of reflection
Define 'Refraction'
The change in direction of a wave as it enters a medium at an angle to a boundary
What happens when a wave bends away from a normal?
It speeds up
What happens when a when bends towards a normal?
It slows down
Define 'Diffraction'
The spreading of a wave as it passes through a gap or around an edge
How is diffraction affected when entering a different sized gap
-The larger the gap the smaller the diffraction effect, however the smaller the gap the greater the diffraction effect
How is diffraction affected when wavelength changes magnitude
- The greater the wavelength, the greater the diffraction effect
-The smaller the wavelength, the smaller the diffraction effect
What 2 things occur during refraction
- Wave Speed changes
- Wave direction changes (Unless it travels along a medium)
Give the formula for refractive index
(Speed of light in a vaccum) / (Speed of light in the material)
What is snell's law?
(n1 * sinΘ1) = (n2 * SinΘ2)
Give a feature about frequency
frequency always remains constant
Define 'Coherence'
Where 2 waves have a constant phase difference and same frequency
Define 'Interference'
Where 2 or more waves of the same type interact in the same place
What is the principle of superposition
When 2 or more waves of the same type exist at the same place, the resultant wave will be found by adding the displacments of each individual wave.
Under what condition can you only calculate real resultant using superposition
The 2 waves must be coherent
Give 3 features of 'Constructive interference'
- The waves wavelength is always a whole number
- The path difference is (0, 360, 720 etc)
- The phase difference is (0π, 2π, 4π etc)
Give 3 features of 'Desturctive Interference'
- The waves wavelengths are always half numbers (i.e 1/2λ, 3/2λ)
- Their path difference is(180, 540, 900 etc)
- Their phase difference is(π, 3π, 5π etc)
What is young and double's slit equation to find wavelength
λ = (a*x) / d
a = The distance between the separated slits
x = The distance between the separated fringes(distance between the centre of pattern and 1st bright edge)
d = The distance between the screen and slit
In young's double slit equation what is x/d equivalent to
The angle between the centre of pattern and the 1st bright edge (A * sin θ)
Define a 'polarized wave'
A wave with oscillations only in one plane
define an 'unpolarized wave'
A wave with oscillations in all possible planes
What's the only type of wave that can be polarized
EM waves
What is the diffraction grating equation?
n * λ = a * Sinθ
n - The order number
λ - Wavelength
a - Distance between separation of slits
Sinθ - The angle between the normal and maxima
How do you get the distance between the slits?
a = 1 / N
a - Distance between slit separation
N - No of slits per metre
How do you calculate the angle for each order
θ = tan^-1( h/D)
θ - Angle of order
h - Distance between maxima(distance between orders)
D - Distance beween the slits and screen
In a diffraction grating experiment , what can you use to focus the laseer beam on the double slit
Use a single slit
Define a Standing wave
A wave where energy is stored & not transferred
Define a Progressive wave
A wave where energy is transferred from one position to another
Define a node
Points on a stationary wave where there's no displacement of particles
Define an Anti-Node
Points on a stationary wave where the displacement of particles varies by the maximum
Define Phase difference
The difference in displacement of particles along a wave or in 2 waves
Where does constructive interference occur
Where a wave from source 1 arrives at the same point in its cycle as a wave from source 2
Where does destructive interference occur?
Where a wave from source 1 arrives at a different point in its cycle to a wave from source 2
How can a stationary wave be produced with a microwave
Use a microwave transmitter, and use a metal plate for it to reflect the microwave. The initial wave and reflected wave superpose to make a stationary wave
How can you make a stationary wave
- Use a string, use a pulley to hold the string tight
- Use a vibrator to cause oscillations
- The initial wave is reflected bak by the pulley
- The two waves superpose to create a stationary wave
In termsof amplitude what is the difference between stationary waves and progressive waves
-Progressive waves have the same amplitude at all points
-Stationary waves have different amplitudes depending on the
amount of superposition
How does a metal grille polarise a microwave
The electrons in the metal grille absorb the electric field in the same direction as the grille
Give the wavelengths of each wave in the EM spectrum
Radiowaves - 10^2
Microwaves = 10^-2
Infrared = 10^-4
Visiblelight = 0.5 * 10^-6
UV light = 10^-8
X-Rays = 10^-10
Gamma rays = 10^-12
For constructive interference give the equation for path difference
Path difference = n * λ
- n is the order number