Q. A star is moving away from earth and shift in spectral line of wavelength $5700\,\mathring{A}$ is $1.90 \,\mathring{A}$. Velocity of the star is :

Wave Optics Report Error

A

$50 \,km \,s ^{-1}$

B

$70\, km\, s ^{-1}$

C

$80\, km \,s ^{-1}$

D

$100\, km\, s ^{-1}$

Solution:

By Doppler's effect in light shift in wavelength is given as
$\Delta \lambda=\frac{v}{c} \lambda $
$\Rightarrow v=\frac{c \Delta \lambda}{\lambda} $
$\Rightarrow v=\frac{3 \times 10^{8} \times 1.9 \times 10^{-10}}{5700 \times 10^{-10}}$
$=100\, km \,s ^{-1}$

Questions from Wave Optics

1. Critical angle for certain medium is $Sin ^{-1}$ $(0.6)$. The polarizing angle of that medium is .......

KCET 2010

2. Which of the following phenomena support the wave theory of light ?
(a) scattering
(b) interference
(c) diffraction
(d) velocity of light in a denser medium is less than the velocity of light in the rarer medium

KCET 2013

3. In Young's double slit experiment, how many maxima can be obtained on a screen (including central maxima), if $\text{d} = \frac{5 \lambda }{2}$ (where $\lambda $ is the wavelength of light)?

NTA Abhyas 2020

4. Interference fringes are being produced on screen $X Y$ by the slits $S_{1}$ and $S_{2} .$ In figure, the correct fringe locus is

5. Light of wavelength $600 \, nm$ is incident normally on a slit of width $0.2 \, mm$ . The angular width of central maxima in the diffraction pattern is (measured from minimum to minimum)

NTA Abhyas 2020

Physics Most Viewed Questions

1. A car starts from rest and accelerates at $5\, m / s ^{2}$ At $t=4\, s$, a ball is dropped out of a window by a person sitting in the car. What is the velocity and acceleration of the ball at $t =6\, s$ ? (Take $\left. g =10\, m / s ^{2}\right)$

NEET 2021 Motion in a Straight Line

2. If $E$ and $G$ respectively denote energy and gravitational constant, then $\frac{ E }{ G }$ has the dimensions of:

NEET 2021 Physical World, Units and Measurements

3. The de Broglie wavelength of an electron moving with kinetic energy of $144 \,eV$ is nearly

NEET 2020 Dual Nature of Radiation and Matter

4. A wheel with $20$ metallic spokes each $1\, m$ long is rotated with a speed of $120\, rpm$ in a plane perpendicular to a magnetic field of $0.4\, G$. The induced emf between the axle and rim of the wheel will be, $(1 G = 10^{-4}\, T)$

NEET 2020 Electromagnetic Induction

5. Calculate the acceleration of the block and trolly system shown in the figure The coefficient of kinetic friction between the trolly and the surface is $0.05. (g = 10 \,m/s^{2}$, mass of the string is negligible and no other friction exists

NEET 2020 Laws of Motion