\[\Delta y=\frac{\lambda L}{d}\]
Variables
dy[Δy]fringe spacing
lambda[λ]wavelength
Ldistance from slits to screen
dslit separation
Description
What is this formula?
This formula calculates the spacing between adjacent bright fringes in a double-slit interference pattern. The fringe spacing increases with wavelength and screen distance, and decreases when the slit separation becomes larger.
When to use it
Use this formula for double-slit interference experiments when the screen is far from the slits and the small-angle approximation is valid.
Example
Given:
λ=6.0×10^-7 m
L=2.0 m
d=3.0×10^-4 m
Formula:
Δy=λL/d
Substitution:
Δy=(6.0×10^-7)(2.0)/(3.0×10^-4)
Result:
Δy=0.004 m
Applications
- Double-slit experiments
- Wave optics
- Laser interference
- Wavelength measurement
- Optical laboratory analysis