Q
What is the approximate minimum source-to-reflector distance for a distinct echo in air?
RRB Group-D
23/10/2018 (Shift-III)
2018
✓ Answer:
C
17 m
Using a minimum delay of 0.1 s and speed near 340 m/s gives d = vt/2 ≈ 17 m. Options A and B are duplicated in the source.