Question

Even in absolutely clear water, a diver cannot see very clearly because 

A. rays of lights get diffused 

B. velocity of light is reduced in water 

C. ray of light passing through the water makes it turbid. 

D. The focal length of the eye lens in water gets changed and the image is no longer focused sharply on the retina.

Answer 1

When we are underwater, incoming light rays are hardly bent, or focused, at all. Our eye lens is designed to see in air. The eye lens bends the rays a little, but due to the lost corneal refraction, the light that reaches the retina isn't focused and thus cannot see very clearly underwater even if the water is absolutely clear. Hence diver observes a blurred vision.