A large glass slab of thickness 8 cm is placed over a point source of light on a plane surface. It is seen that light emerges out of the top surface of the slab from a circular area of radius . What is the value of ?
Answer: 6
Solution
Light emerges only within the critical angle cone. The critical angle is:
Therefore:
The radius of the circular area is:
The answer is 6.
Therefore:
The radius of the circular area is:
The answer is 6.
JEE Advanced · 2010 · 11 Apr 2010 · Paper 2 · Integer answer