- Young’s double-slit experiment gave definitive proof of the wave character of light.
- An interference pattern is obtained by the superposition of light from two slits.
- In double-slit diffraction, constructive interference occurs when , where d is the distance between the slits, is the angle relative to the incident direction, and m is the order of the interference.
- Destructive interference occurs when .
- Interference from multiple slits () produces principal as well as secondary maxima.
- As the number of slits is increased, the intensity of the principal maxima increases and the width decreases.
- When light reflects from a medium having an index of refraction greater than that of the medium in which it is traveling, a phase change (or a shift) occurs.
- Thin-film interference occurs between the light reflected from the top and bottom surfaces of a film. In addition to the path length difference, there can be a phase change.