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question_answer1)
Two Polaroids are placed in the path of unpolarised beam of intensity \[{{I}_{0}}\] such that no light is emitted from the second Polaroid. If a third polaroid whose polarization axis makes an angle \[\theta \] with the polarization axis of first polaroid, is placed between these polaroids then the intensity of light emerging from the last polaroid will be
A)
\[\left( \frac{{{I}_{0}}}{8} \right){{\sin }^{2}}2\theta \] done
clear
B)
\[\left( \frac{{{I}_{0}}}{4} \right){{\sin }^{2}}2\theta \] done
clear
C)
\[\left( \frac{{{I}_{0}}}{2} \right){{\cos }^{4}}2\theta \] done
clear
D)
\[{{I}_{0}}{{\cos }^{4}}\theta \] done
clear
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question_answer2)
A single slit of width a is illuminated by violet light of wavelength 400 nm and the width of the diffraction pattern is measured as y. When half of the slit width is covered and illuminated by yellow light of wavelength 600 nm, the width of the diffraction pattern is
A)
The pattern vanishes and the width is zero done
clear
B)
\[y/3\] done
clear
C)
3y done
clear
D)
None of these done
clear
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question_answer3)
In the Young's double slit experiment, if the phase difference between the two waves interfering at a point is\[\phi \], the intensity at that point can be expressed by the expression
A)
\[I=\sqrt{{{A}^{2}}+{{B}^{2}}{{\cos }^{2}}\varphi }\] done
clear
B)
\[I=\frac{A}{B}\cos \varphi \] done
clear
C)
\[I=A+B\cos \frac{\varphi }{2}\] done
clear
D)
\[I=A+B\cos \] done
clear
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question_answer4)
The wave front of a light beam is given by the equation \[x+2y+3x=c\](where c is arbitrary constant), then the angle made by the direction of light with the y-axis is
A)
\[{{\cos }^{-1}}\frac{1}{\sqrt{14}}\] done
clear
B)
\[{{\sin }^{-1}}\frac{2}{\sqrt{14}}\] done
clear
C)
\[{{\cos }^{-1}}\frac{2}{\sqrt{14}}\] done
clear
D)
\[{{\sin }^{-1}}\frac{3}{\sqrt{14}}\] done
clear
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question_answer5)
Two beams of light having intensities \[I\] and 4\[I\] interfere to produce a fringe pattern on a screen. The phase between the beams is \[\pi /2\] at point A and \[\pi \] at point B. Then, the difference between the resultant intensities at A and B is
A)
\[2I\] done
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B)
\[4I\] done
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C)
\[5I\] done
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D)
\[7I\] done
clear
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question_answer6)
In the adjacent diagram, CP represents a wave front and AO and BP, the corresponding two rays. Find the condition on \[\theta \] for constructive interference at P between the ray BP and reflected ray OP
A)
\[\cos \theta =3\lambda /2d\] done
clear
B)
\[\cos \theta =\lambda /4d\] done
clear
C)
\[\sec \theta -\cos \theta =\lambda /d\] done
clear
D)
\[\sec \theta -\cos \theta =4\lambda /d\] done
clear
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question_answer7)
In a double-slit experiment, instead of taking slits of equal width, one slit is made twice as wide as the other. Then in the interference pattern
A)
The intensities of both the maxima and the minima increase done
clear
B)
The intensity of the maxima increases and the minima has zero intensity done
clear
C)
The intensity of the maxima decreases and that of the minima increases done
clear
D)
The intensity of the maxima decreases and the minima has zero intensity done
clear
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question_answer8)
In Young's double-slit experiment, the slits are illuminated by monochromatic light. The entire set-up is immersed in pure water. Which of the following act cannot restore the original fringe width?
A)
Bringing the slits close together. done
clear
B)
Moving the screen away from the slit plane. done
clear
C)
Replacing the incident light by that of longer wavelength. done
clear
D)
Introducing a thin transparent slab in front of one of the slits. done
clear
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question_answer9)
In a two-slit experiment with white light, a white fringe is observed on a screen kept behind the slits. When the screen in moved away by 0.05 m, this white fringe
A)
Does not move at all done
clear
B)
Gets displaced from its earlier position done
clear
C)
Becomes colored done
clear
D)
Disappears done
clear
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question_answer10)
In the ideal double-slit experiment, when a glass plate (refractive index 1.5) of thickness \[t\] is introduced in the path of one of the interfering beams (wavelength\[\lambda \]), the intensity at the position where the central maximum occurred previously remains unchanged. The minimum thickness of the glass plate is
A)
\[2\lambda \] done
clear
B)
\[2\lambda /3\] done
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C)
\[\lambda /3\] done
clear
D)
\[\lambda \] done
clear
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question_answer11)
In Young's double-slit experiment, the angular width of a fringe formed on a distant screen is \[1{}^\circ .\] The wavelength of light used is\[6000\,\,\overset{\text{o}}{\mathop{\text{A}}}\,\]. What is the spacing between the slits?
A)
344 mm done
clear
B)
0.1344 mm done
clear
C)
0.0344 mm done
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D)
0.034 mm done
clear
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question_answer12)
A plane wave front \[(\lambda =6\times {{10}^{-7}}m)\] falls on a slit 0.4 mm wide. A convex lens of focal length 0.8 m placed behind the slit focusses the light on a screen. What is the linear diameter of second maximum?
A)
6 mm done
clear
B)
12 mm done
clear
C)
3 mm done
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D)
9 mm done
clear
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question_answer13)
Two Nicols are oriented with their principal planes making an angle of\[60{}^\circ \]. The percentage of incident unpolarized light which passes through the system is
A)
50 % done
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B)
100 % done
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C)
12.5 % done
clear
D)
37.5 % done
clear
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question_answer14)
Blue light of wavelength 480 nm is most strongly reflected off a thin film of oil on a glass slab when viewed near normal incidence. Assuming that the index of refraction of the oil is 1.2 and that of the glass is 1.6, what is the minimum thickness of the oil film (other than zero)?
A)
100 nm done
clear
B)
200 nm done
clear
C)
300 nm done
clear
D)
None of these done
clear
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question_answer15)
A monochromatic beam of light falls on YDSE apparatus at some angle (say\[\theta \]) as shown figure. A thin sheet of glass is inserted in front of the lower slit\[{{s}_{2}}\]. The central bright fringe (path difference = 0) will be obtained
A)
At O done
clear
B)
Above O done
clear
C)
Below O done
clear
D)
Anywhere depending on angle\[\theta \], thickness of plate t, and refractive index of glass\[\mu \] done
clear
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question_answer16)
In a standard Young's double-slit experiment with coherent light of wavelength 600 nm, the fringe width of the fringes in the central region (near the central fringe,\[{{P}_{0}}\]) is observed to be 3 mm. An extremely thin glass plate ' is introduced in front of the first slit, and the fringes are observed to be displaced by 11 mm. Another thin plate is placed before the second slit and it is observed that the fringes are now displaced by an additional 12 mm. If the additional optical path lengths introduced are \[{{\Delta }_{1}}\] and \[{{\Delta }_{2}}\] then
A)
\[11{{\Delta }_{1}}=12{{\Delta }_{2}}\] done
clear
B)
\[12{{\Delta }_{1}}=11{{\Delta }_{2}}\] done
clear
C)
\[11{{\Delta }_{1}}>12{{\Delta }_{2}}\] done
clear
D)
None of the above done
clear
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question_answer17)
In Young's double slit experiment, one of the slit is wider than other, so that amplitude of the light from one slit is double of that from other slit. If \[{{I}_{m}}\] be the maximum intensity, the resultant intensity \[I\] when they interfere at phase difference \[\phi \] is given by
A)
\[\frac{{{I}_{m}}}{9}(4+5cos\phi )\] done
clear
B)
\[\frac{{{I}_{m}}}{3}\left( 1+2co{{s}^{2}}\frac{\phi }{2} \right)\] done
clear
C)
\[\frac{{{I}_{m}}}{5}\left( 1+4co{{s}^{2}}\frac{\phi }{2} \right)\] done
clear
D)
\[\frac{{{I}_{m}}}{9}\left( 1+8co{{s}^{2}}\frac{\phi }{2} \right)\] done
clear
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question_answer18)
Assuming human pupil to have a radius of 0.25 cm and a comfortable viewing distance of 25 cm, the minimum separation between two objects that human eye can resolve at 500 nm wavelength is
A)
\[1\mu m\] done
clear
B)
\[30\mu m\] done
clear
C)
\[100\mu m\] done
clear
D)
\[300\mu m\] done
clear
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question_answer19)
In a YDSE bichromatic lights of wavelengths 400 nm and 560 nm are used. The distance between the slits is 0.1 mm and the distance between the plane of the slits and the screen is 1 m. The minimum distance between two successive regions of complete darkness is
A)
4 mm done
clear
B)
5.6 mm done
clear
C)
14 mm done
clear
D)
28 mm done
clear
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question_answer20)
In a YDSE light of wavelength\[\lambda =5000\]\[\overset{\text{o}}{\mathop{\text{A}}}\,\]is used which emerges in phase from two slits a distance \[d=3\times {{10}^{-7}}m\] apart. A transparent sheet of thickness\[t=1.5\times {{10}^{-7}}m\], is refractive index n = 1.17, is placed over one of the slits. Where does the central maxima of the interference now appear?
A)
\[\frac{D(\mu -1)t}{2d}\] done
clear
B)
\[\frac{2D(\mu -1)t}{d}\] done
clear
C)
\[\frac{D(\mu +1)t}{d}\] done
clear
D)
\[\frac{D(\mu -1)t}{d}\] done
clear
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question_answer21)
In a single slit diffraction experiment first minimum for red light (660 nm) coincides with first maximum of some other wavelength\[\lambda \]. What is the value of\[\lambda \] (in\[\overset{\text{o}}{\mathop{\text{A}}}\,\])?
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question_answer22)
A flake of glass (refractive index 1.5) is placed over one of the openings of a double slit apparatus. The interference pattern displaces itself through seven successive maxima towards the side where the flake is placed, if wavelength of the diffracted light is \[\lambda \] = 600 nm, then find the thickness (in nm) of the flake.
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question_answer23)
In a two slit experiment with monochromatic light fringes are obtained on a screen placed at some distance from the sits. If the screen is moved by \[5\times {{10}^{-2}}\]m towards the slits, the change in fringe width is \[3\times {{10}^{-5}}\]m. If separation between the slits is \[{{10}^{-3}}\] m, find the wavelength (in\[\overset{\text{o}}{\mathop{\text{A}}}\,\]) of light.
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question_answer24)
Two coherent sources \[{{s}_{1}}\] and \[{{s}_{2}}\] are separated by a distance four times the wavelength \[\lambda \] of the source. The sources lie along y axis whereas a detector moves along + x axis. Leaving the origin and far off points the number of points where maxima are observed is ______.
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question_answer25)
A ray of light of intensity \[I\]is incident on a parallel glass-slab at a point A as shown in figure. It undergoes partial reflection and refraction. At each reflection 25% of incident energy is reflected. The rays AB and A?B? undergo interference. The ratio \[{{I}_{\max }}/{{I}_{\min }}\]is
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