Oscillations/Wave Motion Flashcards
Define simple harmonic motion
Defined as a periodic motion where the acceleration’s object must always be directly proportional and opposite to the displacement from it’s equilibrium position
Define the equilibrium position for wave motion
The midpoint of oscillation. The position where no net force acts on the particle.
Define the displacement for simple harmonic motion
The distance from its equilibrium position in a specific direction.
Define amplitude of simple harmonic motion
The maximum displacement from its equilibrium position.
Define velocity of a particle in simple harmonic motion
The instantaneous velocity of the particle.
At which position does the minimum speed of the particle occur, amplitude or equilibrium positions?
Amplitude position
At which position does the maximum speed of the particle occur, the amplitude or equilibrium positions?
Equilibrium
Define the acceleration of a particle in simple harmonic motion.
The instantaneous acceleration of the particle
At which position does the minimum magnitude of acceleration occur, the amplitude or equilibrium positions?
Equilibrium position
At which position does the maximum magnitude of acceleration occur, the amplitude or equilibrium positions?
Amplitude position
Define the period of an oscillation
The time taken for the particle to complete one oscillation
Define the frequency of an oscillation.
The number of oscillations performed per unit time
Define phase/phase angle + the phase angle of one full cycle of an oscillation.
Phase/phase angle is the stage of oscillation the particle is in at a particular instant.
In one full cycle of an oscillation, the phase angle is 360° (2π rad), which also means it’s 0 rad since it reverts back to its original position.
Define angular frequency of a particle in simple harmonic motion
The product of 2π and the frequency of oscillation of the body in simple harmonic motion
At which position does max KE/min PE occur
The equilibrium position
At which position does min KE/max PE occur
The amplitude positions
What happens in a free oscillation?
The body oscillates under a resisting force only, without any external or resistive force acting on it; and the total energy of the oscillating body stays constant.
Define damped oscillation
An oscillation where it’s amplitude gradually decreases as the body loses energy due to resistive forces.
Define forced oscillating system
The body oscillates under a periodic driving force from a driver, where there is continuous energy input to the oscillating body.
What are the 3 features of a resonance curve?
Curves shifted lower with increased damping (amplitude gets smaller)
Flatter peak at resonance with increased damping.
Peak is skewed to the left with increased damping.
Define wave.
A wave is a propagation of a disturbance which transfers energy from one point to another without the physical transfer of matter.
Define a progressive wave
Waves that transfer energy from one point to another without the transfer of matter.
Define a transverse wave.
a wave where particles vibrate in a direction perpendicular to the direction of propagation of energy
Define a longitudinal wave.
A wave where particles oscillate to the direction of propagation of the wave.
Define the speed of a wave.
The distance travelled by the wave over the time taken.
Define wavefront
The imaginary line joining all the points of the wave that have the same phase.
Define the ray of a wave.
A ray is the line drawn in the direction of the wave motion which is used to indicate the path taken by the wave.
Define the intensity of a wave
The rate of transfer of energy per unit area perpendicular to the direction of the wave.
The 6 formulae for intensity of a wave
E/tA
P/A
P/(4πr^2)
P/(2πr)
kA^2
K(f^2)(A^2)
Define polarization of a wave
The process whereby vibration of the particles of a transverse wave occurs in a single plane only, and the direction of the vibrations are perpendicular to the direction of propagation of the plane.
Malu’s law
The intensity of a beam of plane-polarized light after passing it through a polarizer varies with the square of the cosine of the angle through which the polarizer is rotated from the position that gives maximum intensity.
Formula for the intensity of a transmitted wave (through a polarizer)
I = I(max) (cos theta)^2
The resultant amplitude A of light transmitted through a polarizer:
A = A(max) (cos theta)^2
For an oscillating body, state what is meant by forced frequency.
The frequency at which the body is made to vibrate or oscillate when a periodic external force acts on it.
For an oscillating body, state what is meant by natural frequency of vibration
The frequency at which the body is made to vibrate or oscillate freely without any extreme or resistive force acting on it.
For an oscillating body, state what is meant by resonance.
Resonance is the maximum transfer of energy from the driver to the body during a forced oscillation, where the body oscillates with max amplitude, and when the driving frequency is equal to the natural frequency of vibration.
State and explain one situation where resonance is useful
Cooking of food using microwave oven: microwaves having a frequency the same as the natural frequency of vibration of water molecules in food is used to cook the food
State and explain one situation where resonance should be avoided.
On vibrating machinery parts, metal panels on the body of a washing machine resonates when driving frequency of the rotating drum is equal to the natural frequency of the panel.
What happens during light damping
The amplitude of oscillations gradually decreases with time but the period remains constant.
For an oscillating body, state what is meant by free oscillations
The body oscillates under a restoring force only without any external or resistive force acting on it
Define forced oscillations in an oscillating system
The body oscillates under a periodic driving force from a driver where there is continuous energy input in a body.
Why can’t sound waves be polarized?
Sound waves are longitudinal waves which cannot be polarized no matter how the transmission axis of the polarizer is oriented, because the direction of vibrations of sound waves are parallel to the direction of propagation.
For sound waves in the gas, state the origin of the energy in the wave.
The mechanical energy (KE and PE) of the vibrating source that produces the wave
For sound waves in the gas, state the origin of the restoring force on a molecule as it vibrates.
The intermolecular forces between the neighbouring molecules to bring them back to equilibrium position.
Explain why the intensity of a minimum is never zero.
As microwaves travel away from the source/gets reflected, the waves lose energy and amplitude decreases.
Minimum corresponds to a node. When incident microwaves of relatively larger amplitudes superimpose with reflected microwaves of smaller amplitudes, resultant displacement ≠ 0 since it’s unable to cancel out.
As I is proportional to A², intensity at a minimum is never zero.
Prove SHM using equations
ΣF= ma
K(eo - x) - mg = ma where mg = keo
-kx = ma
a = (-k/m)x
Derive v = fλ
speed = distance/time taken
v = d/t = λ/T = fλ
Order of magnitude of wavelengths in the electromagnetic spectrum
Radio > 1x10^-1
Micro 1x10^-3 to 1x10^-1
Infrared 7x10^-7 to 1x10^-3
Visible 4x10^-7 to 7x10^-7
Ultraviolet 1x10^-9 to 4x10^-7
X ray 1x10^-11 to 1x10^-9
Gamma < 1x10^-11
