Physics 5 - Waves and the Particle Nature of Night (AS)
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- Created by: Alexander Hyde
- Created on: 09-04-22 11:03
What is the difference between a progressive wave and a standing wave?
A progressive wave transfers energy while a standing wave does not.
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What is the definition of displacement?
How far a point on the wave has moved from its undisturbed position.
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What is the definition of amplitude?
The maximum magnitude of displacement (e.g. from peak to the undisturbed position). Given the symbol A
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What is the definition of a wavelength?
The length of one wave cycle (e.g. from crest to crest). Given the symbol λ
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What is the definition of a period?
The time for one whole cycle to pass through a point. Given the symbol T and measured in seconds.
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What is the definition of frequency?
The number of cycles per second passing a point. Given the symbol 'f' and measured in Hertz (Hz)
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What is the definition of phase?
A measurement of the position of a wave along its wave cycle.
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What is the definition of phase difference?
The amount that one wave 'lags' behind one another. Measured in degrees or radians.
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What is the equation that links frequency and period?
f = 1/T
f = Frequency (Hz)
T = Period (s)
f = Frequency (Hz)
T = Period (s)
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What is the wave equation?
wavespeed (v) = Frequency (f) * Wavelength (λ)
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What are the features of a transverse wave?
- Vibration at right angles to the direction of wave propagation
- Represented as a sine wave
All EM waves are transverse waves
- Represented as a sine wave
All EM waves are transverse waves
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What are the features of a longitudinal wave?
Compressions and refractions of a medium.
Pressure variations in the medium. At some points, the molecules are closer together so there is increased pressure.
Sound waves are the most common type of longitudinal wave.
Pressure variations in the medium. At some points, the molecules are closer together so there is increased pressure.
Sound waves are the most common type of longitudinal wave.
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What is the definition of reflection?
When a wave bounces back after hitting a boundary.
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What is the definition of refraction?
A wave changes direction when passing through a medium. This is due to the change in velocity of the wave because it is going into a material of a different optical density.
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What is the definition of intensity?
Rate of flow of energy per unit of area at right angles to the direction of travel of the wave.
Intensity = Power/Area
I = P/A
Intensity = Power/Area
I = P/A
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What relationship links intensity and amplitude
The intensity of a wave is proportional to the amplitude squared of a wave.
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What happens when a wave is polarised?
The wave will only oscillate in one direction. Usually, a wave oscillates in many directions.
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What does a polarising filter do?
Transmits vibrations only in one direction.
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What happens to a light wave when it is reflected?
It is partially polarised. This can be used to remove unwanted reflections in photography and in polarised sunglasses to remove glare.
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What happens when a wave is superimposed?
The displacements of each wave combine. e.g. two crests make a large crest and a crest and a trough council out a wave.
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What is the difference between constructive and destructive interference?
Constructive - Two similar points on a wave combine to make a bigger wave (e.g. two crests)
Destructive - Two opposite points on a wave combine to cancel each other out.
If the two points are not equal, then the interference is not total.
Destructive - Two opposite points on a wave combine to cancel each other out.
If the two points are not equal, then the interference is not total.
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What is the definition of coherence?
Two waves have the same wavelength and frequency and a fixed phase difference between them.
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How is a stationary (standing) wave formed?
The superposition of two progressive waves with the same wavelength moving in opposite directions.
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What are the features of stationary waves on strings?
Nodes and antinodes - Where the amplitude is zero and at its maximum respectively
Resonant frequencies - An exact number of half wavelengths fit onto the string.
Resonant frequencies - An exact number of half wavelengths fit onto the string.
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What is the lowest possible resonant frequency also called?
The fundamental mode of vibration or the first harmonic
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What does the refractive index measure?
How much a material slows down light.
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How is the refractive index of a material calculated?
n = c/v
n = refractive index
c = speed of light in a vacuum (3.0x10^8 ms-1)
v = Speed of light in the material
n = refractive index
c = speed of light in a vacuum (3.0x10^8 ms-1)
v = Speed of light in the material
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What is snell's law?
Using angles to calculate the refractive index of a material.
n1sinx1 = n2sinx2
n1sinx1 = n2sinx2
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What is the definition of the critical angle?
Where the angle of refraction is greater than or equal to 90 degrees. The light is reflected along the boundary and does not leave the material.
Total internal reflection occurs beyond this point.
Total internal reflection occurs beyond this point.
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How do you calculate a critical angle?
sin C = 1/n
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What is the difference between convex and concave lenses?
Convex lenses bring light together to the principal axis while a concave lens bends light away.
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What is the difference between a real and virtual image?
Real - The image is there and can be captured on a screen.
Virtual - The image can't be captured on a screen because the light rays aren't really where the image appears to be.
Virtual - The image can't be captured on a screen because the light rays aren't really where the image appears to be.
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What is the lens equation?
1/f = 1/u + 1/v
f = focal length
u = distance between object and lens
v = distance between image and lens
f = focal length
u = distance between object and lens
v = distance between image and lens
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What is the equation for the power of a lens?
P = 1/f
When lenses are touching the equation is:
P = P1 + P2 + P3
When lenses are touching the equation is:
P = P1 + P2 + P3
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What is the equation for magnification?
m = image height/object height
m = v/u
m = v/u
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What happens when a wave is diffracted?
The wave is spread out as they come through a narrow gap or as they pass around obstacles.
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How does diffraction change depending on the size of the gap?
As the gap gets closer to the size of the wavelength, the wave is diffracted more.
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What is Huygens' construction?
Every point on a wavefront is considered to be a source of secondary wavelets that spread out in the forward direction at the speed of the wave.
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What is an interference pattern?
Alternating bands of constructive and destructive interference. If you are using light waves, they will manifest as light and dark bands.
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What is the equation for diffraction gratings?
nλ = dsinx
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What general conclusions can be drawn from this equation?
If the wavelength is bigger, the more spread out the pattern.
If d is bigger, the less the pattern is spread out.
Values of sinx greater than 1 are impossible so for certain n, it is impossible.
If d is bigger, the less the pattern is spread out.
Values of sinx greater than 1 are impossible so for certain n, it is impossible.
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What does the wave/particle duality show?
That light can behave as a wave and as a particle (a photon).
Light can produce interference and diffraction patterns and produce the photoelectric effect.
Light can produce interference and diffraction patterns and produce the photoelectric effect.
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What is the Planck constant value?
6.636x10^-34 J s
Given the symbol h
Given the symbol h
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What shows that photons exist in discrete energy levels?
The equation E = hc/λ
Only certain values are allowed.
Only certain values are allowed.
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What defines the electronvolt?
The kinetic energy gained by an electron when it is accelerated through a potential difference of 1 volt so one electronvolt is equal to 1.60x10^-19 Joules.
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What are the features of an emission spectra?
Lines of different colours which represent corresponding wavelengths of light on a dark background.
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What can we do with emission spectras?
Use them to identify elements. Each element has a unique structure so each element's emission spectra will be different to any other.
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What is the photoelectric effect?
When light is shone on a metal plate, photoelectrons can be released if the light has a high enough frequency. This frequency usually falls within the UV range.
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What is the work function?
The energy needed to break the bonds holding the electrons to the plate. Its given the symbol Φ.
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What is the equation that links frequency and the work function?
f = Φ/h
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What happens to the spare energy that is not used to break the bonds of the electrons?
It is given as kinetic energy to the electron.
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What is the equation that describes the photoelectric effect?
hf = Φ +1/2mv^2
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What is the De Broglie Equation?
λ = h/p
λ = Wavelength
h = Planck's constant
p = Momentum of the particle
λ = Wavelength
h = Planck's constant
p = Momentum of the particle
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Other cards in this set
Card 2
Front
What is the definition of displacement?
Back
How far a point on the wave has moved from its undisturbed position.
Card 3
Front
What is the definition of amplitude?
Back
Card 4
Front
What is the definition of a wavelength?
Back
Card 5
Front
What is the definition of a period?
Back
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