Waves 2 Flashcards
Principle of superposition of waves
When two similar types of waves meet at a point, the resultant displacement at a point is equal to the sum of the displacements of the individual waves
Interference
Superposition of two progressive waves from coherent sources to produce a resultant wave with displacement equal to the sum of the displacements from the two waves
Coherence
Two wave sources or waves that are coherent have a constant phase difference
Path difference
The difference in the distance travelled by two waves from their source to a specific point
Constructive interference
2nπ phase difference
nλ path difference
Destructive interference
(2n+1)π phase difference
(n+1/2)λ path difference
Two-source interference for sound and microwaves / Young double-slit experiment using visible light (superposition experiments)
As the microphone/microwave detector/your eyes move from A to B, a series of maximum and minimum intensities is detected.
This is because the path difference of the waves from the two coherent sources varies.
When it is nλ, there is constructive interference and a maximum forms; when it is (n+1/2)λ, destructive interference occurs and a minimum forms.
Stationary wave
A wave that remains in a constant position with no net transfer of energy and is characterised by its nodes and antinodes - also called a standing wave
Node
For a stationary wave, a point where the amplitude is always zero
Antinode
For a stationary wave, a point where the amplitude is the always the greatest
Stationary waves using microwaves and stretched strings
A progressive wave is transmitted (along a taut string) by a vibrator/microwave transmitter and is reflected back by a pulley/metal sheet; incident wave and reflected wave have the same frequency/COHERENT.
Waves superpose and form a stationary wave.
Always destructively to form nodes, and always constructively to produce antinodes. (Can be detected by microwave detector by moving across)
