Wave & Wave Motion Study Flashcards
Define Mechanical Waves
A Travelling Mechanical Wave is a disturbance carrying energy through a medium without any overall movement of that medium.
E.g. Water waves, Sound waves, Waves on a rope, Ultrasound waves
Define Electromagnetic Waves
Electromagnetic waves are energy transmitted from one place to another at the Speed of Light.
Do not need medium.
Define a Wave
A wave is a means of transferring energy from one place to another by oscilation.
Define Transverse Waves
A Transverse Wave is a wave where the direction of vibration is Perpendicular to the direction in which the wave travels.
E.g. Water, On a rope, Electromagnetic
Define Longitudinal Waves
A Longitudinal Wave is a wave where the direction of vibration is Parallel to the direction in which the wave travels.
E.g. Compression on a spring, Sound, Ultrasonic
Define Frequency
The Frequency (f ) is the number of cycles passing per second.
A cycle is from one crest to the next or one trough to the next.
Define Wavelength
The Wavelength (λ) is the distance from any point on one cycle to the corresponding point on the next cycle.
Define Velocity (Waves)
The Velocity (v) of a wave is the distance travelled by one cycle in one second.
Define Amplitude
The Amplitude (A) of a wave is the maximum distance of any point from its undisturbed position.
Amplitude is not always measured as a distance. When a sound wave passes through the air - amplitude can be measured as the difference in pressure in the air at the peak of the wave compared with pressure before the sound wave was created.
Formula for Frequency
Velocity = Frequency x Wavelength
or
c = fλ
Name the Wave Phenomena
5 of them
Reflection
Refraction
Diffraction
Interference
Polarisation
Reflection
Occurs when bouncing off a barrier
Reflection off parabola results in convergence at one point
Used in Sonar & Radar
Refraction
Happens when travelling from one medium to another.
Accompanied by change in direction, wavelength and speed. No change in frequency.
Diffraction
Is the spreading out of a wave when it passes through a gap or passes by an obstacle.
Is only significent when the width of the gap is similar in size to the wavelength of the wave.
Is the bending of waves around obstacles and openings.
Increasing wavelength means increasing diffraction.
Interference
Is the phenomenon that occurs when two waves meet while travelling along the same medium.
Constructive Interference
If the amplitude of the new wave is greater than the individual waves, Constructive Interference occured.
Destructive Interference
If the amplitude of the new wave is less than the individual waves, Destructive Interference occured.
Coherent Sources
Two sources are Coherent if the waves from each source are in phase or have a constant phase difference between them.
If this is so, they must also have the same frequency.
Polarisation
If the vibrations of a transverse wave are confined to one plane only, that wave is said to be Polarised
Stationary Waves
When two periodic travelling waves of the same frequency and amplitude moving in opposite directions meet, they interfere with each other.
The resulting wave formed is called a Stationary Wave (or a standing wave).
Doppler Effect
The apparent change in the frequency of waves due to the relative motion of the source or the observer is called the Doppler Effect.
When source moves toward the observer, the observed frequency is higher.
When source moves away from the observer, the observed frequency is lower.
Formula For Frequency of waves from a moving source
Moving Towards: f ‘ = fc / c-u
Moving away: f ‘ = fc / c+u
f ‘ is observed frequency
f is actual frequency
c is speed of the wave
u is speed of the source
