Will give brainiest to best answer You are standing outside when the sky goes dark.

t

Explanation:

As per the the question the sound source is the mosquito.

the mosquito produces the sound with the help of its wings

as per the question the wings vibrate at the rate of 500 vibrations per second.

we have been asked to calculate the time period  of vibration.

we know that that time period is the reciprocal of frequency of vibration

hence time period [T]=

                                   =

                                   =

                                   =0.002 second

hence the time period of the  vibration of the wings of the mosquito is 0.002 second.