Question

What is the effect on time period of initial displacement slightly change?

Answer 1

it is the answer for the question.

Answer 2

The classroom answer (which is probably what you want) is nothing. That is, the period is unaffected by a change in the amplitude. This is what Galileo noticed, which led to the invention of the pendulum clock.

The exact answer is that there is a slight change in period which is barely perceptible for small amplitudes. The error increases with increasing amplitude. But you aren't supposed to know this until you are at a more advanced level.✔✔✔✔✔✔