interference when two light waves meet, their amplitudes add (by principle of superposition) and...
TRANSCRIPT
Interference When two light waves meet, their amplitudes add (by principle of
superposition) and the resulting disturbance can be either reinforced (constructive interference) or eliminated (destructive interference).
Constructive interference.When the crest of one wave passes through, or is super positioned upon, the crest of another wave, we say that the waves constructively interfere. Constructive interference also occurs when the trough of one wave is super positioned upon the trough of another wave
Phenomena of constructive interference During any wave interference
the shape of the medium is determined by the sum of the separate amplitudes of each wave. We often say that when waves interfere, amplitudes add.
Using the arrow buttons step through the above animation to see how the amplitudes add during constructive interference. Notice that in this animation the crest of the red wave constructively interferes with the crest of the blue wave.
Destructive Interference
When the crest of one wave passes through, or is super positioned
upon, the trough of another wave, we say that the waves destructively
interfere.
Young’s Double Slit Experiment The narrow slits, S1 and
S2 act as sources of waves
The waves emerging from the slits originate from the same wave front and therefore are always in phase
Resulting interference The light from the two slits form a visible pattern on a
screen The pattern consists of a series of bright and dark parallel
bands called fringes Constructive interference occurs where a bright fringe
occurs Destructive interference results in a dark fringe
Interference Patterns The upper wave has to
travel farther than the lower wave
The upper wave travels one wavelength farther
Therefore, the waves arrive in phase
A bright fringe occurs
Interference Patterns The upper wave travels
one-half of a wavelength farther than the lower wave
The trough of the bottom wave overlaps the crest of the upper wave (180 phase shift)
This is destructive interference
A dark fringe occurs
Application of Interference in CD`s
Data is stored digitally A series of ones and zeros read by laser light
reflected from the disk Strong reflections correspond to constructive
interference These reflections are chosen to represent zeros
Weak reflections correspond to destructive interference These reflections are chosen to represent ones
Applications
Michelson-Morley: Evidence of Special Relativity Lab work: Density of Air Detection of gravitational waves