Question

ultraviolet way sent from the ship and reaches back in 4 seconds if speed is ultraviolet rays is 1600
per second in water calculate the distance ship and point of reflection

Answer 1

Firstly i think you have written the speed wrong.It should be 1600 m/s.
We know,
Here,
s=2d/t
where d is distance, t is time in which rays reach back after reflection, s is speed
So,
1600=2d/4
d=(1600×4)/2
=3200unit

Hope it helps....