If in a simple pendulum experiment the length of the inextensible string is increased by a factor of four, its period is increased by a factor of?

A.

4

B.

\(\frac{\pi}{2}\)

C.

\(\frac{1}{4}\)

D.

2

Correct answer is D

In a simple pendulum, T = 2\(\pi\)\(\sqrt{\frac{L}{g}}\)

\(\frac{T_1}{T_2} = \sqrt{\frac{L_1}{L_2}}\)  but L\(_2\) = 4L\(_1\) 

\(\frac{T_1}{T_2} = \sqrt{\frac{L_1}{4L_1}}\)

T\(_2\) = 2T\(_1\)