A sine wave has a period of 5 msec. What is the frequency?

200 Hz

Explanation:

The period of a sine wave is 5 milliseconds.

That means the each cycle in the wave takes up 5 milliseconds.

So the frequency of the wave is the inverse of the time period, namely, 1 / (5 * 10 ^ - 3)

=1000/5 = 200 per second or 200 Hertz.

So the frequency of the wave will be 200 Hertz which means that the wave will complete 200 cycles per second. Larger the time period, lower is the frequency and vice versa.