A sound wave is direct at a wall. In 20 seconds, 200 wave cycles hit the wall.
what is the frequency and period.

Frequency=10 Hz

Period=0.1 s

Explanation:

Frequency of a wave is the number of complete cycles per unit time. Usually, frequency is cycles per second, with unit as Heartz

Given cycles of the wave as 200 and time as 20 seconds

Frequency=200÷20=10 cycles per second

Therefore, frequency is 10 Hz

Period is usually the reviprocal of frequency hence reciprocal of 10 Hz will be 1/10=0.1 s

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.

305.7

explanation:

density =m/v

density =917/3.00

density = 305.

approximately = 305.7

in four significant figures