Answer:
[tex]1.4\cdot 10^6 Hz[/tex]
Explanation:
The relationship between the frequency, the wavelength and the speed of a wave is given by the wave's equation:
[tex]v=f \lambda[/tex]
where
v is the speed of the wave
f is the frequency
[tex]\lambda[/tex] is the wavelength
For the pulse in this problem,
[tex]\lambda = 1.0 mm = 0.001 m\\v = 1400 m/s[/tex]
Solving for f, we find the frequency:
[tex]f=\frac{v}{\lambda}=\frac{1400}{0.001}=1.4\cdot 10^6 Hz[/tex]
