**Category:** Wave Physics  
**Subtype:** Interference of Waves  
**Problem Description:** This problem involves the interference of two coherent waves on the surface of water. It asks for the condition under which the amplitude at certain points in the interference pattern is at a minimum. Specifically, it requires finding the path difference (\(\Delta d\)) between the two waves that results in destructive interference (minimum amplitude).  

**Key Concept:** Destructive interference occurs when the path difference between two waves is an odd multiple of half the wavelength.