Answer: 
Explanation:
Given
mass of ball m=10 kg
It is placed at a height of 150 m
It is dropped from the height and allowed to free fall for 40 m
Velocity acquired by the ball during this fall is given by 
Insert u=0, a=g

Kinetic energy at this instant

Wavelength = (speed) / (frequency)
Wavelength = (340 m/s) / (400 /s)
<em>Wavelength = 0.85 meter</em>