White light may be considered to be a mixture of waves with rangi… - Vidyadip

MCQ

White light may be considered to be a mixture of waves with $\lambda$ ranging between $3900 \mathring A$ and $7800 \mathring A$. An oil film of thickness 10,000 $\mathring A$ is examined normally by reflected light. If $\mu=1.4$, then the film appears bright for

✓
$4308 \mathring A, 5091 \mathring A, 6222 \mathring A$
B
$4000 \mathring A, 5091 \mathring A, 5600 \mathring A$
C
$4667 \mathring A, 6222 \mathring A, 7000 \mathring A$
D
$4000 \mathring A, 4667 \mathring A, 5600 \mathring A, 7000 \mathring A$

✓

Answer

Correct option: A.

$4308 \mathring A, 5091 \mathring A, 6222 \mathring A$

The film appears bright when the path difference $(2 \mu t \cos r)$ is equal to odd multiple of $\frac{\lambda}{2}$
i.e. $2 \mu t \cos r=(2 n-1) \lambda / 2 \quad$ where $n=1,2,3 \ldots$.
$\therefore \lambda=\frac{4 \mu t \cos r}{(2 n-1)}$
$=\frac{4 \times 1.4 \times 10,000 \times 10^{-10} \times \cos 0}{(2 n-1)}=\frac{56000}{(2 n-1)} \mathring A $
$\therefore \lambda=56000\ \mathring A ,18666\ \mathring A, 8000\ \mathring A, 6222\ \mathring A, 5091\ \mathring A, $
$4308\ \mathring A, 3733\ \mathring A .$
The wavelength which are not within specified range are to be refracted.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "MCQ" from Wave Optics→Wave Optics — all question types→JEE physics STD 12 Science question papers→CBSE Board STD 12 Science question papers→CBSE Board question paper generator→

Similar questions

Water rises in a vertical capillary tube upto a height of $2.0 \mathrm{~cm}$. If the tube is inclined at an angle of $60^{\circ}$ with the vertical, then upto what length the water will rise in the tube

Eddy currents are used in

A particle, initially at rest on a frictionless horizontal surface, is acted upon by a horizontal force which is constant in size and direction. A graph is plotted between the work done $(W)$ on the particle, against the speed of the particle, $(v)$. If there are no other horizontal forces acting on the particle the graph would look like

A body freely falling from the rest has a velocity ' $v$ ' after it falls through a height ' $h$ '. The distance it has to fall down for its velocity to become double, is

A coil of inductance $L$ has an inductive reactance of $X_L$ in an $AC$ circuit in which the effective current is $l$. The coil is made from a super$-$conducting material and has no resistance. The rate at which power is dissipated in the coil is

An astronomical telescope has an angular magnification of magnitude $5$ for distant objects. The separation between the objective and the eye piece is $36 \mathrm{~cm}$ and the final image is formed at infinity. The focal length $f$ of the objective and the focal length $f$ of the eye piece are

An ideal gas heat engine operates in Carnot cycle between $227^{\circ} \mathrm{C}$ and $127^{\circ} \mathrm{C}$. It absorbs $6 \times 10^4 \mathrm{cals}$ of heat at higher temperature. Amount of heat converted to work is

A body falls freely from rest. It covers as much distance in the last second of its motion as covered in the first three seconds. The body has fallen for a time of

A bomb of mass $30 \mathrm{~kg}$ at rest explodes into two pieces of masses $18 \mathrm{~kg}$ and $12 \mathrm{~kg}$. The velocity of $18 \mathrm{~kg}$ mass is $6 \mathrm{~ms}^{-1}$. The kinetic energy of the other mass is

For the structural analysis of crystals, $X$-rays are used because