In a two-slit interference experiment, constructive interference occurs when two light waves from the slits meet in phase, meaning their crests and troughs align. This causes the amplitudes to add up, resulting in bright fringes on the screen.
The condition for constructive interference is:
- The path difference between the two waves must be an integer multiple of the wavelength.
This means:
- The waves must travel distances that differ by 0, 1, 2, 3, … whole wavelengths.
Under this condition, the waves reinforce each other, producing regions of maximum intensity.
Key factors affecting constructive interference:
- Wavelength of the light used,
- Distance between the slits,
- Screen distance from the slits,
- And the position where the bright fringe appears.
In summary, constructive interference results in the bright bands (or maxima) seen in the interference pattern due to the waves arriving in phase.