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Title: IB Physics Topic 4 Notes
Description: Notes for Topic 4 (Wave Physics) of IB Physics.
Description: Notes for Topic 4 (Wave Physics) of IB Physics.
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4
...
A simple harmonic oscillation is oscillatory motion in which the acceleration is opposite and proportional to displacement from equilibrium
...
The time taken to complete a cycle is a period
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The reciprocal, the number of cycles per unit time is the frequency
w is angular speed
Topic 4 Page 2
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Qualitatively describing the energy changes
Because there is no motion yet, there is no kinetic energy
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A continuous exchange between EK and EP occurs
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EK + EP = ET
Topic 4 Page 3
SHM x/v/a Graphs
• The graph of x vs t is reflected across the axis in order to get a vs t graph
Phase and Phase difference
The three graphs are sinusoidal (they take the shape of a sine wave)
...
The graphs have a phase difference
...
When the phase difference is 0 or T then two systems are oscillating in phase
...
The total energy of the system:
m = 125 g
Spring constant :
Acceleration of mass at
(Hooke's Law)
Topic 4 Page 5
SHM Force vs Displacement graph
From a Force vs Displacement graph we can determine:
Explain that the mass is undergoing Simple Harmonic Motion:
• In SHM,
...
• The graph shows that
...
The spring constant of the spring:
Pick any
and any
...
0 kg
The maximum speed of the mass:
The speed of the mass at
m:
Topic 4 Page 6
4
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Propagation is when a wave travels
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Radiation means any disturbance that propagates outwards from its source
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Energy is the ability to move an object
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All waves that require a material object as the medium are called mechanical waves
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The particles within
the medium oscillate back and forth, staying more or less in the same location, while the wave propagates over long distances
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- The particles of the medium vibrate about their rest position at the same frequency as the source
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(e
...
Slinky wave)
- In two-dimensional (2-D) wave motion, the wave is only restricted to travelling along the surface of the medium
...
g
...
(e
...
sound of bomb)
Topic 4 Page 8
Wavelength, frequency, period and wave speed
Wavelength (λ) is the shortest distance between two points that are in phase on a wave, i
...
two consecutive crests or two consecutive troughs
...
(measured in
Hz)
Period (T) is the time that it takes for one complete wavelength to pass a fixed point or for a
particle to undergo one complete oscillation
...
The speed of the wave (v) is equal to the frequency multiplied by the wavelength
...
A longitudinal wave is a wave that has the direction of particle oscillation parallel to the energy transfer
...
EM radiation has electric and magnetic fields at right angles to each other and also to the direction of
propagation of the wave
...
Distance vs Displacement Dot graph
Can be converted to:
Rarefaction is positive, compression is negative
Compression is when the particles are more bunched up than normal
...
Topic 4 Page 12
Interpreting Graphs
Amplitude
Wavelength
Period
Frequency and wave speed can be calculated
...
3 - Wave Characteristics
Topic 4 Page 15
Wavefronts and Rays
Wavefronts are surfaces on which all points have the same phase
...
Characteristics of wavefronts:
• Wavefronts can be 3D
• The farther the wavefronts get from the source the more it becomes flat
• Wavefronts can be bent by obstacles in the environment or by the properties of the medium through
which the wave passes
...
Topic 4 Page 16
Amplitude and Intensity
Intensity is the rate energy is being transmitted per unit area and is measured in (W m -2)
...
Ewave Amplitude2
Inverse Square Law:
Topic 4 Page 17
Superposition
Wave superposition is the addition of two or more waves passing simultaneously through a medium
...
Superposition is also called interference and can be constructive o r destructive
...
Polarisation only applies to transverse waves
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The light is polarized when the E-fields of the light are all oriented in a
single direction
...
The second filter is called the analyser
...
Topic 4 Page 19
Problems Involving Malus's Law
The transmitted intensity of polarised light through a polariser is reduced by a factor of
Malus law:
Question: State what is meant by polarised light [1 mark]
• Light sources produce waves having E-fields in many directions (important to say this in every polarisation question)
• Polarized light has waves that have their E-fields in one direction
Topic 4 Page 20
Methods of Polarisation
Besides a polaroid filter, there are other ways to polarise light
...
Partially polarised light is
made
...
4 - Wave Behaviour
Topic 4 Page 22
Reflection & Refraction
Reflection occurs when a wave meets a boundary such as a solid object
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During reflection the frequency and the wavelength of the wave do not change
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Refraction changes the direction of the incident ray
...
Topic 4 Page 23
Snell's Law
Snell's law relates the wave's velocities in two mediums to their angles
...
(not in data booklet)
...
Snell's law can be expanded
...
Topic 4 Page 24
Diffraction
Diffraction takes place when a wave with wavelength equal to or larger than the size of an aperture or an obstacle moves
through or past the aperture or obstacle
...
If the wavelength is smaller than the aperture, then there will be minimal to no diffraction
...
Diffraction explains why we can hear but cannot see around
corners
...
Topic 4 Page 25
Interference Patterns
Wave interference is a phenomenon that occurs when two waves meet while traveling along the same medium
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Constructive interference occurs at any location along the medium where the two interfering waves have a displacement in the same direction
...
Topic 4 Page 26
Double-slit Interference
The path difference:
when it's a bright fringe (maxima)
when it's a dark fringe (minima)
is the order of the band
...
Topic 4 Page 27
Total Internal Reflection
The total internal reflection occurs when there is no refracted ray because the angle of incidence is greater than the critical angle
...
The critical angle is the angle of incidence for which the angle of refraction is 90°
...
Topic 4 Page 28
4
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The resulting wave has a
displacement that is the sum of the displacements of the travelling waves
...
Instead, it has sections that either grow or shrink
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A point with maximum displacement is called an antinode
...
A standing wave does not transfer
energy
...
The amplitude of the sound wave would double and
the volume will increase
...
Resonance is when something causes the wave to have higher amplitudes at specific frequencies
...
If the path length difference is equal to
, , then the two waves will be out of phase and destructively interfere
...
Topic 4 Page 30
Boundary Conditions
When you pluck a stringed instrument, waves travel to the ends of the string and reflect at each end, and return to
interfere under precisely the conditions needed for a standing wave
...
Conditions for open or closed on both ends (Or Strings):
Conditions for different ends:
Topic 4 Page 31
Solving Problems
1
...
3
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Identify given information
Identify what ends it is
Identify which harmonic they're asking for
Solve for answer
Topic 4 Page 32
Title: IB Physics Topic 4 Notes
Description: Notes for Topic 4 (Wave Physics) of IB Physics.
Description: Notes for Topic 4 (Wave Physics) of IB Physics.