What happens to the frequency if the period were to change from o.2 seconds to 0.5 seconds

The Hz would change

Explanation:

For example, a wave with a time period of 2 seconds has a frequency of 1 ÷ 2 = 0.5 Hz.

your answer is "the 1950's"

it takes hundreds of years to become stable.

if you have another question lmk.