Answer:
[tex]\lambda=4000\ km[/tex]
Explanation:
It is given that,
Frequency for submarine communications, f = 76 Hz
We need to find the wavelength of those extremely low-frequency waves. the relation between the wavelength and the frequency is given by :
[tex]c=f\times \lambda[/tex]
[tex]\lambda=\dfrac{c}{f}[/tex]
[tex]\lambda=\dfrac{3\times 10^8\ m/s}{76\ Hz}[/tex]
[tex]\lambda=3947368.42\ m[/tex]
[tex]\lambda=3947\ km[/tex]
or
[tex]\lambda=4000\ km[/tex]
So, the wavelength of those extremely low-frequency waves is 4000 km. Hence, this is the required solution.