Question 248: Wave Optics

Question

A ray of light from a monochromatic point source of light is incident at a point on the screen. If a thin mica film of thickness ' $t$ ' and refractive index ' $n$ ' is introduced in its path, then the optical path

Accepted Answer

Step 1: Concept of optical path length
The optical path length (OPL) is given by:
$ 	ext{OPL} = n 	imes 	ext{geometrical length travelled in medium}. $
So, if a distance $t$ in air is replaced by $t$ in a medium of refractive index $n$:
OPL in air: $= 1 \cdot t = t$.
OPL in mica: $= n \cdot t$.
Step 2: Change in OPL
Difference due to insertion:
$ \Delta (	ext{OPL}) = ( n t - t ) = (n - 1)t. $
So the OPL is
increased
by $(n-1)t$.
Step 3: Correct option
Option D
: increased by $(n-1)t$. Ã¢ÂÂ
Final Answer:
$ \boxed{	ext{The optical path is increased by } (n-1)t.} $

Answer

is decreased by $(\mathrm{n}-1) \mathrm{t}$.

Answer

is increased by $(\mathrm{n}+1) \mathrm{t}$.

Answer

is not affected.

Answer

is increased by $(\mathrm{n}-1) \mathrm{t}$.

Wave Optics

A ray of light from a monochromatic point source of light is incident at a point on the screen. If a thin mica film of thickness ' t ' and refractive index ' n ' is introduced in its path, then the optical path

Choose the correct answer: