Question

please answer in details answer is 0.8s but I need in a process

Answer 1

1st time the pendulums moving process duration is 0.2 s but it move toward the side to side it duration will be changed to high

Answer 2

time period is the time taken to complete one to and fro movement of bob . so this means that from mean position to one extreme end time taken is 0.2 s so one complete revolution contains 4 times movement from mean to extreme position .so answer is 4times time taken to complete one part that is 4*0.2= 0.8.