Correct option is C)
In the question, the wavelength (λ) is given as 20 cm, that is, 0.20 m and the wave velocity, v is given as 24 m/s.
The frequency ν, velocity v and wavelength λ relation is given as:
ν=
λ
v
.
Number of waves produced in one second is called as frequency, i.e. ν=
λ
v
=ν=
0.20
24
=120 waves per second.
Time period of a wave is given as the inverse of frequency.
That is, T=
ν
1
=
120
1
=8.33×10
−3
seconds
Hence, the time period of the wave is given as 8.33×10
−3
seconds.