University Physics Volume 3

# Summary

## 3.1Young's Double-Slit Interference

• Youngâ€™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.

## 3.2Mathematics of Interference

• In double-slit diffraction, constructive interference occurs when $dsinÎ¸=mÎ»(form=0,Â±1,Â±2,Â±3â€¦)dsinÎ¸=mÎ»(form=0,Â±1,Â±2,Â±3â€¦)$, where d is the distance between the slits, $Î¸Î¸$ is the angle relative to the incident direction, and m is the order of the interference.
• Destructive interference occurs when $dsinÎ¸=(m+12)Î»form=0,Â±1,Â±2,Â±3,â€¦dsinÎ¸=(m+12)Î»form=0,Â±1,Â±2,Â±3,â€¦$.

## 3.3Multiple-Slit Interference

• Interference from multiple slits ($N>2N>2$) 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.

## 3.4Interference in Thin Films

• When light reflects from a medium having an index of refraction greater than that of the medium in which it is traveling, a $180Â°180Â°$ phase change (or a $Î»/2Î»/2$ 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.

## 3.5The Michelson Interferometer

• When the mirror in one arm of the interferometer moves a distance of $Î»/2Î»/2$ each fringe in the interference pattern moves to the position previously occupied by the adjacent fringe.
Order a print copy

As an Amazon Associate we earn from qualifying purchases.