Huygens' Principle

Q. For a transparent medium, relative permeability, ${\mu }_r=1.0$ and relative permittivity, ${ϵ}_r=1.44$. The velocity of light in this medium will be -

1. $2.5\times {10}^8\text{m/s}$
2. $3.0\times {10}^8\text{m/s}$
3. $2.8\times {10}^8\text{m/s}$
4. $2.7\times {10}^8\text{m/s}$

Q. A beam of light of wavelength 600 nm from a distance source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between the first dark fringes on either side of the central bright fringe is:

1. 1.2 cm
2. 1.2 mm
3. 2.4 cm
4. 2.4 mm

Q. An electromagnetic wave of frequency $v$ = $3.0$ $MHz$ passes from vacuum into a dielectric medium with relative permittivity $\epsilon$ = $4$. Then,

1. Wavelength is doubled and frequency becomes half.
2. Wavelength is halved and frequency remains unchanged.
3. Wavelength and frequency both remains unchanged.
4. Wavelength is doubled and frequency remains unchanged.

Q.

If youngs double-slit experiment is performed in water instead of air, then

1. No fringes would be seen

2. Fringe width would decrease

3. Fringe width would increase

4. Fringe width would remain unchanged

Q.

The filament of a light bulb has a surface area $64m{m}^2$. The filament can be considered as a black body at temperature $2500K$emitting radiation like a point source when viewed from far. At night the light bulb is observed from a distance of$100m$. Assume the pupil of the eyes of the observer to be circular with radius $3mm$. Then

1. Power radiated by the filament is in the range$642W$ to $645W$

2. Radiated power entering into one eye of the observer is in the range $3.15\times {10}^{-8}W$ to $3.25\times {10}^{-8}W$

3. The wavelength corresponding to the maximum intensity of light is $1160nm$

4. Taking the average wavelength of emitted radiation to be $1740nm$, the total number of photons entering per second into one eye of the observer is in the range $2.75\times {10}^{11}$ to $2.85\times {10}^{11}$

Q.

Is anything faster than light ?

Q. A light wave travelling linearly in a medium of dielectric constant $4$, incidents on the horizontal interface separating medium with air. The angle of incidence for which the total intensity of incident wave will be reflected back into the same medium will be:
(Given : relative permeability of medium ${\mu }_r=1$)

1. ${20}^{\circ }$
2. ${10}^{\circ }$
3. ${30}^{\circ }$
4. ${60}^{\circ }$

Q.

Electromagnetic waves travelling in a medium which has relative permittivity $1.3$ and relative permeability $2.14$ speed of electromagnetic waves in this medium will be _________

1. $3.6\times {10}^8\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

2. $1.8\times {10}^8\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

3. $1.8\times {10}^6\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

4. $13.6\times {10}^6\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

Q. Light of wavelength lamda enters a medium with refractive index n2 from a medium with refractive index n1.What is the wave lenght in second medium?

Q. Calcuate the wavelenght of spectral line in lyman series corresponding to n2=3

Q. What is relation between wavelength and dispersion?

Q. (a) Define wavefront. Use Huygens' principle to verify the laws of refraction.
(b) How is linearly polarised light obtained by the process of scattering of light ? Find the Brewster angle for air-glass interface, when the refractive index of glass =1.5.

Q. A mixture of yellow light of wavelength $3800\stackrel{\circ }{A}$ and blue light of wavelength $4000\stackrel{\circ }{A}$ is incident normally on air film of 0.00019 mm thickness. The colour of reflected light is:

1. grey
2. red
3. blue
4. violet

Q. A spherical convex surface of radius of curvature $10\text{cm}$ has object and image in mediums of refractive index $1.0$ and $\frac{4}{3}$ respectively. Its power will be

1. $+4\text{D}$
2. $+6\text{D}$
3. $+1\text{D}$
4. $+3.33\text{D}$

Q. Find number of electrons emitted per second by a 24 W source of monochromatic light of wavelength 6600 10-10 assuming 3% efficiency for photoelectric effect h= 6.610-34

Q.

A young's double slit apparatus has slits separated by 0.28 mm and a screen 48 cm away from the slits. The whole apparatus is immersed in water and the slits are illuminated by the red light ($\lambda =700$ nm in vacuum) find th efringe-width of the pattern formed on the screen.

Q. The ratio of wavelength of 1st line of balmer series and that of second line of Lyman series, in hydrogen spectrum is

Q. The Balmer series for the $H$-atom can be observed

1. in any transition in a $H$-atom.
   
2. if we measure the frequencies of light emitted when an excited atom falls to the ground state.
   
3. if we measure the frequencies of light emitted due to transitions between excited states and the first excited state.
   
4. ​​​​​as a sequence of frequencies with the higher frequencies getting closely packed.

Q.

The idea of secondary wavelets for the propagation of a wave was first given by

1. Fresnel

2. Newton

3. Huygen

4. Maxwell

Q.

Who discovered the wave particle duality of light?

Q. At t = 0, a transverse wave pulse in a wire is described by the function
$y=\frac{6}{(x^2-3)}$ where x and y are in metres. The function y(x, t) that describes this wave equation if it is travelling in the positive x direction with a speed of 4.5 m/s is

1. 
2. 
3. 
4. 

Q. The plane wavefront shown in the diagram is travelling from air to water. $LM$ is the incident wavefront and $L^{\prime }{M}^{\prime }$ is the refracted wavefront. The wavefront $LM$ is obliquely incident on the surface of water at an angle of incidence ${60}^{\circ }$. If the distance $M{M}^{\prime }=10\text{cm}$, find distance $L{L}^{\prime }$. Take refractive index of water equal to $\frac{4}{3}$.

1. $30\text{cm}$
2. $40\text{cm}$
3. $13.33\text{cm}$
4. $7.5\text{cm}$

Q. A: The corpuscular theory fails in explaining the velocities of light in air and water.
B: According to corpuscular theory, the light should travel faster in a 'denser medium than in a rarer medium.

1. If both A and B are true but the B is the correct explanation of A
2. If both A and B are true but the B is not the correct explanation of A
3. If A is true but B is false
4. If both the A and B are false
5. If B is true but A is false

Q. 2 particles are oscillating along two close parallel straight lines side by side, with the same frequency and amplitudes.They pass each other, moving in opposite directions when their displacement is half of amplitude.The mean position of the two particles lie on a straight line perpendicular to the path of two particles. The phase difference is?

Q.

Which of the following phenomena takes place inside an optical fiber?

1. Total internal reflection

2. Scattering

3. Diffraction

4. Refraction

Q.

Who first proposed that light was wave-like in character?

1. Huygens

2. Newton

3. Young

4. Maxwell

Q.

Write a short note on the speed of light.

Q. A plane wavefront travelling in a straight line in a vacuum encounters a medium of refractive index $\mu$. At $P$, the shape of the wavefront is :

1. 
2. 
3. 
4. 

Q. The Euler bucking load for a long slender column with fixed end condition is 10000 N. If the end condition are changed to fixed free, Euler bucking load (in N) would be

1. 5000
2. 2500
3. 1250
4. 625

Q. What is wavefront? Explain laws of refraction of light on the bases of Huygens wave theory.