Interference/Diffraction with shadows

[Aeighme]

Homework Statement

At 11:00hrs a vertical stick in air, 1.8 m long, casts a shadow 1.2 m long. If the same stick is placed at 11:00hrs in air in a flat bottomed pool of salt water half the height of the stick, how long is the shadow on the floor of the pool? (For this pool, n = 1.56.)

Homework Equations

Not sure=/

The Attempt at a Solution

Don't know where to begin >.<

 

[cepheid]

sounds like more of a *refraction* problem than an interference/diffraction problem. In other words, I think you can do this problem using only geometric optics, without considering the wave nature of light.

So, ask yourself, what *happens* to a ray of light upon entering the water that would tend to change the nature of the shadow cast by the stick? Strong hint: the length of the shadow is determined by the angle of the light source.