Question

A travelling microscope is focussed on a mark on a piece of paper and the scale reading is A. A rectangular block of glass is placed on the paper and the microscope is raised and focussed the mark on the paper, then microscope reading is B. A layer of lycopodium powder is sprinkled on the block of glass, the reading now is C. The refractive index of the material of the block is

• A. $\frac{C-B}{C-A}$
• B. $\frac{C-A}{C-B}$
• C. $\frac{C-A}{B-A}$
• D. $\frac{C}{C-A}$

Answer 1

Answer: (B)

$\frac{C-A}{C-B}$

The refractive index of the glass slab will be equal to,

$\mu =\frac{RealDepth}{Apparentdepth}$

Now, for the given case, Real Depth = C - A

Apparent depth = C - B

Thus, $\mu =\frac{C-A}{C-B}$