Chapter 13 - Vibrations and Waves - Learning Path Questions and Exercises - Exercises - Page 484: 5

Decrease of $2.0s$

$T=\frac{1}{f}$ If the frequency is doubled, then the period is halved. When the frequency is increase from 0.25 Hz to 0.50 Hz, the period decreases from $\frac{1}{0.25}=4s$ to $\frac{1}{0.5}=2s$ So, there is decrease of $2.0s$