Concepts Of Physics MCQ Edition [Volume 1]PhysicsDispersion and Spectra
Two identical thin crown glass prisms, each with a refracting angle A , and a thin flint glass prism of refracting angle A' , are combined together. The flint glass prism is situated inverted between the two crown glass prisms. The refractive indices of the crown glass for red, yellow, and violet rays are _r , _y , and _v respectively, while those for the flint glass are _r' , _y' , and _v' respectively. Determine th
Options
- A2( _y - 1) _y' - 1
- B_y - 1 2( _y' - 1)
- C2( _y' - 1) _y - 1
- D_y' - 1 2( _y - 1)
Correct answer
A. 2( _y - 1) _y' - 1
Step-by-step solution
The deviation produced by a thin prism of refracting angle A and refractive index is given by = ( - 1)A . For the two identical crown glass prisms, the total deviation for the yellow ray is: _c = 2( _y - 1)A For the inverted flint glass prism, the deviation is in the opposite direction. The deviation for the yellow ray is: _f = ( _y' - 1)A' For no net deviation of the yellow ray, the total deviation must be zero, which implies: _c = _f Substituting the expressions for deviations, we get: 2( _y - 1)A = ( _y' - 1)A'