Interference and diffraction Flashcards
All waves can?
Reflect, Refract, Diffract
Diffraction in long and short wavelengths
Long wavelengths diffract more than shorter wavelengths
What is interfernce?
When two waves meet they may combine to produce a new pattern
What is coherence?
constant phase relationship
To observe interference patterns, the waves must come from?
coherent sources
Constructive Interference?
Waves meet in phase (crest meets crests / trough meets trough).
This results in an increase in amplitude
Destructive Interference?
Waves meet out of phase (crest meets trough)
This results in a reduced (or zero) amplitude.
Interference Pattern?
When light from two coherent sources interferes, it produces a pattern of constructive and destructive interference.
A bright fringe or maximum occurs when?
the waves meet in phase and constructive interference has taken place
A dark fringe or minimum occurs when?
the waves meet out of phase and destructive interference has taken place
Path difference in maximum?
whole number of wavelenght
Path difference in minimum?
half number of wavelenths
Fringe separation can be increased by?
increasing wavelength
decreasing slit separation
increasing the distance between the slits and the screen
diffraction grating can be used to?
to make an interference pattern brighter and more spaced out
Key features of the white light interference pattern (grating)
The central fringe is white as for all colours of light the path difference is zero.
Violet light has a shorter wavelength than red light so violet light pattern is less spread out than for red light.
Many spectra produced, symmetrical about the central maximum.
