Question

Two identical light sources \(S_1\) and \(S_2\) emit light of same wavelength \(\lambda\). These light rays will exhibit interference if

• A. their phase differences remain constant
• B. their phases are distributed randomly
• C. their light intensities remain constant
• D. their light intensities change randomly

Hint:

Interference is observed only when two sources are coherent, i.e., they maintain a constant phase difference.

Answer 1

The Correct Option is A

Step 1: Condition for sustained interference.
For stable (sustained) interference, the two sources must be coherent.
Coherent sources are those which:
- have the same frequency (same wavelength)
- maintain a constant phase difference
Step 2: Check options.
Option (A): Constant phase difference \(\Rightarrow\) coherent \(\Rightarrow\) interference possible.
Option (B): Random phase \(\Rightarrow\) no stable interference pattern.
Option (C): Constant intensity alone cannot guarantee interference.
Option (D): Random intensities destroy pattern.
Final Answer: \[ \boxed{\text{their phase differences remain constant}} \]