Wave Interference

Step 1: Understanding the Fringe Formula
In Young’s double-slit experiment, the fringe width ( ) is given by: where:
- = Wavelength of light (in meters),
- = Distance between slits and screen (in meters),
- = Distance between the two slits (in meters),
- = Fringe width (in meters).
Step 2: Given Data
- Distance between the slits: mm m,
- Distance to the screen: m,
- Distance between central bright fringe and fourth bright fringe: Since this corresponds to the fourth bright fringe, we use:
Step 3: Calculating Fringe Width

Step 4: Calculating Wavelength
Rearranging the fringe width equation: Substituting values:
Step 5: Conclusion
Since m is 6000 nm, the correct answer is 6000 nm.

Step 1: Understanding Wavefronts
A wavefront is defined as the locus of all points in a medium that vibrate in the same phase. It represents the points where the wave has the same displacement and motion characteristics.
Step 2: Phase Difference in a Wavefront
- The phase difference between two points in a wave is given by: where:
- is the phase difference,
- is the wavelength,
- is the distance between the two points along the wave propagation. - However, in a given wavefront, all particles oscillate in phase, meaning:
Step 3: Conclusion
Since all points on a wavefront oscillate together, the phase difference between any two particles on the same wavefront is zero.