The phenomenon of persistence of sound due to multiple reflections is called MCQ with Answer and Explanation

Explanation:
Enrico Fermi led the team that constructed 'Chicago Pile-1', which achieved the world's first artificial, self-sustaining nuclear chain reaction on December 2, 1942. This was the first nuclear reactor. While he worked on the Manhattan Project (atomic bomb), his crowning individual distinction is creating the first controlled reactor.

Explanation:
Frequency (f) is defined as the number of complete oscillations or cycles a wave makes in one second (measured in Hertz). The Time period (T) is the time taken to complete one full oscillation (measured in seconds). They are inversely related: T = 1/f. If a wave has a frequency of 50 Hz, its period is 1/50 seconds.

Explanation:
Total distance = 200 m (forward) + 100 m (back) = 300 m. Total time = 20 s + 10 s = 30 s. Average speed = total distance / total time = 300/30 = 10 m/s. Average velocity would be displacement (200-100=100 m) / 30 s = 3.33 m/s. But average speed is 10 m/s. Wait, 300/30 = 10. But that's option A 10 m/s. I need to check: Did I compute right? 200 m forward, then returns 100 m back, so total path length = 300 m. Time total = 30 s. Average speed = 10 m/s. Option A is 10 m/s, B is 6.67. That gives A. But to test concept, many confuse with velocity. I'll set correct answer A. But I'll adjust to make distinction: Maybe distance first 200 m at 10 m/s, return 100 m at 5 m/s? Already given times. So correct answer A. It's moderate. I'll keep.