Question

Calculate the period of a strobe light flashing $25$ times in $5.0s$.

• A. $5s$
• B. $0.2s$
• C. $3s$
• D. $0.6s$

Answer 1

The correct option is B $0.2s$

The frequency (f) of a wave is the number of full wave forms generated per second. This is the same as the number of repetitions per second or the number of oscillations per second.
Time Period (T) is the number of seconds per waveform, or the number of seconds per oscillation. It is clear that frequency and period are reciprocals.
In this case, a strobe light flashs 25 times in 5.0 seconds..
That is, the frequency is given as $f=\frac{25}{5}=5Hz$.
Time period = $\frac{1}{f}=\frac{1}{5}=0.20s$
Hence, the frequency is 5 Hz and the time period is 0.20 seconds.