Can a Fish see Things Outside the Water?

Most recent answer: 02/03/2010

While doing a problem we hav a question that "Upto what radius of a cone can a fish see from its place.The refractive indices of the medium are given..Assume them as u like"...But my question is we have done the problem by considering the limits upto the critical angle...But inorder the fish to see the outside things the light should enter from outside to inside..That is from rarer medium to denser medium...Then in that case there will be no critical angle..But we considered as the light will be emitted from fish's eye and it will go outside(so it will go from denser to rarere and hence there can be critical angle)...I didnt understand how this is possible..please can you clarify me...
- Prudhvi Raj Borra (age 16)
Machilipatnam,Andhra Pradesh,India
Yes, it can see things at all angles outside the water.  In addition, it can see things inside the water that are reflected from the air-water interface.   This is called 'Total internal reflection'.
There is a wealth of web sites devoted to this subject, just Google 'total internal reflection'.


(published on 02/03/2010)

Follow-up on this answer