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MCQOPTIONS
This section includes 96 Mcqs, each offering curated multiple-choice questions to sharpen your Physics knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
In the spectrum of light of a luminous heavenly body the wavelength of a spectral line is measured to be 4747 Å while actual wavelength of the line is 4700 Å. The relative velocity of the heavenly body with respect to earth will be (velocity of light is \[3\times {{10}^{8}}m/s\]) [MP PMT/PET 1998] |
| A. | \[3\times {{10}^{5}}m/s\]moving towards the earth |
| B. | \[3\times {{10}^{5}}m/s\]moving away from the earth |
| C. | Infrared rays |
| D. | \[3\times {{10}^{6}}m/s\]moving away from the earth |
| Answer» E. | |
| 52. |
Light coming from a star is observed to have a wavelength of 3737 Å, while its real wavelength is 3700 Å. The speed of the star relative to the earth is [Speed of light \[3\times {{10}^{8}}m/s\]] [MP PET 1997] |
| A. | \[3\times {{10}^{5}}m/s\] |
| B. | \[3\times {{10}^{6}}m/s\] |
| C. | \[{{E}_{z}},\,{{B}_{x}}\] |
| D. | \[3.7\times {{10}^{6}}m/s\] |
| Answer» C. \[{{E}_{z}},\,{{B}_{x}}\] | |
| 53. |
A light source approaches the observer with velocity 0.8 c. The doppler shift for the light of wavelength \[5500\,{AA}\] is [MP PET 1996] |
| A. | \[4400\,\,{AA}\] |
| B. | \[1833\,\,{AA}\] |
| C. | Infrared |
| D. | \[7333\,\,{AA}\] |
| Answer» D. \[7333\,\,{AA}\] | |
| 54. |
A star emitting radiation at a wavelength of \[5000\,{AA}\] is approaching earth with a velocity of\[1.5\times {{10}^{6}}m/s\]. The change in wavelength of the radiation as received on the earth, is [CBSE PMT 1995] |
| A. | \[25\,\,{AA}\] |
| B. | Zero |
| C. | Band absorption spectrum |
| D. | \[2.5\,\,{AA}\] |
| Answer» B. Zero | |
| 55. |
If a source of light is moving away from a stationary observer, then the frequency of light wave appears to change because of [AFMC 1995] |
| A. | Doppler's effect |
| B. | Interference |
| C. | a > b, b < c |
| D. | None of these |
| Answer» B. Interference | |
| 56. |
A star is moving away from the earth with a velocity of 100 km/s. If the velocity of light is \[3\times {{10}^{8}}m/s\] then the shift of its spectral line of wavelength\[5700\,\,{AA}\]due to Doppler's effect will be [MP PMT 1994] |
| A. | \[0.63\,\,{AA}\] |
| B. | \[1.90\,\,{AA}\] |
| C. | Carry news |
| D. | \[5.70\,\,{AA}\] |
| Answer» C. Carry news | |
| 57. |
In the context of Doppler effect in light, the term ?red shift? signifies [MP PET 1994] |
| A. | Decrease in frequency |
| B. | Increase in frequency |
| C. | Ozone layer reflects radio waves |
| D. | Increase in intensity |
| Answer» B. Increase in frequency | |
| 58. |
The velocity of light emitted by a source S observed by an observer O, who is at rest with respect to S is c. If the observer moves towards S with velocity v, the velocity of light as observed will be [NCERT 1980] |
| A. | c + v |
| B. | \[c-v\] |
| C. | \[\overrightarrow{E}\times \overrightarrow{B}\] |
| D. | \[\sqrt{1-\frac{{{v}^{2}}}{{{c}^{2}}}}\] |
| Answer» D. \[\sqrt{1-\frac{{{v}^{2}}}{{{c}^{2}}}}\] | |
| 59. |
A star emits light of\[5500\,\,{AA}\]wavelength. Its appears blue to an observer on the earth, it means [DPMT 2002] |
| A. | Star is going away from the earth |
| B. | Star is stationary |
| C. | Reflection |
| D. | None of the above |
| Answer» D. None of the above | |
| 60. |
A light wave is incident normally over a slit of width\[24\times {{10}^{-5}}cm\]. The angular position of second dark fringe from the central maxima is 30o. What is the wavelength of light [RPET 1995] |
| A. | \[6000\,\,{AA}\] |
| B. | \[5000\,\,{AA}\] |
| C. | Radio waves |
| D. | \[1500\,\,{AA}\] |
| Answer» B. \[5000\,\,{AA}\] | |
| 61. |
The radius \[r\] of half period zone is proportional to [RPMT 1998, 2002] |
| A. | \[\sqrt{n}\] |
| B. | \[\frac{1}{\sqrt{n}}\] |
| C. | Blue |
| D. | \[\frac{1}{n}\] |
| Answer» B. \[\frac{1}{\sqrt{n}}\] | |
| 62. |
Radius of central zone of circular zone plate is \[2.3\,mm.\] Wavelength of incident light is \[5893\,\,{AA}.\] Source is at a distance of \[6\,m.\] Then the distance of first image will be [RPMT 2001] |
| A. | \[9\,m\] |
| B. | \[12\,m\] |
| C. | \[3.7\times {{10}^{7}}m/s\] |
| D. | \[36\,m\] |
| Answer» B. \[12\,m\] | |
| 63. |
A zone plate of focal length \[60\,cm,\] behaves as a convex lens, If wavelength of incident light is \[6000\,\,{AA},\] then radius of first half period zone will be [RPMT 2001] |
| A. | \[36\times {{10}^{-8}}m.\] |
| B. | \[6\times {{10}^{-8}}m.\] |
| C. | \[3167\,\,{AA}\] |
| D. | \[6\times {{10}^{-4}}m.\] |
| Answer» E. | |
| 64. |
A plane wavefront \[(\lambda =6\times {{10}^{-7}}m)\] 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 [RPMT 2001] |
| A. | \[6\,mm\] |
| B. | \[12\,mm\] |
| C. | \[100\,\,{AA}\] |
| D. | \[9\,mm\] |
| Answer» B. \[12\,mm\] | |
| 65. |
Figure here shows P and Q as two equally intense coherent sources emitting radiations of wavelength 20 m. The separation PQ is 5.0 m and phase of P is ahead of the phase of Q by 90o. A, B and C are three distant points of observation equidistant from the mid-point of PQ. The intensity of radiations at A, B, C will bear the ratio [NSEP 1994] |
| A. | 0 : 1 : 4 |
| B. | 4 : 1 : 0 |
| C. | Diffraction |
| D. | 2 : 1 : 0 |
| Answer» E. | |
| 66. |
In the Young's double slit experiment, if the phase difference between the two waves interfering at a point is f, the intensity at that point can be expressed by the expression [MP PET 1998; MP PMT 2003] |
| A. | \[I=\sqrt{{{A}^{2}}+{{B}^{2}}{{\cos }^{2}}\varphi }\] |
| B. | \[I=\frac{A}{B}\cos \varphi \] |
| C. | \[3.80\,\,{AA}\] |
| D. | \[I=A+B\cos \varphi \] Where A and B depend upon the amplitudes of the two waves. |
| Answer» E. | |
| 67. |
In an interference arrangement similar to Young's double slit experiment, the slits S1 and S2 are illuminated with coherent microwave sources each of frequency 106 Hz. The sources are synchronized to have zero phase difference. The slits are separated by distance d = 150 m. The intensity I\[(\theta )\]is measured as a function ofq, where q is defined as shown. If I0 is maximum intensity, then \[I(\theta )\] for \[0\le \theta \le {{90}^{o}}\]is given by [IIT 1995] |
| A. | \[I(\theta )={{I}_{0}}\]for \[\theta ={{0}^{o}}\] |
| B. | \[I(\theta )={{I}_{0}}/2\]for \[\theta ={{30}^{o}}\] |
| C. | Decrease in intensity |
| D. | \[I(\theta )\] is constant for all values of q |
| Answer» C. Decrease in intensity | |
| 68. |
A 20 cm length of a certain solution causes right-handed rotation of 38°. A 30cm length of another solution causes left-handed rotation of 24°. The optical rotation caused by 30cm length of a mixture of the above solutions in the volume ratio 1 : 2 is [KCET 2001] |
| A. | Left handed rotation of 14° |
| B. | Right handed rotation of 14° |
| C. | c |
| D. | Right handed rotation of 3° |
| Answer» E. | |
| 69. |
A beam of plane polarized light falls normally on a polarizer of cross sectional area \[3\times {{10}^{-4}}{{m}^{2}}\]. Flux of energy of incident ray in 10?3 W. The polarizer rotates with an angular frequency of 31.4 rad/sec. The energy of light passing through the polarizer per revolution will be |
| A. | 10?4 Joule |
| B. | 10?3 Joule |
| C. | Star is coming towards earth |
| D. | 10?1 Joule |
| Answer» B. 10?3 Joule | |
| 70. |
A beam of natural light falls on a system of 6 polaroids, which are arranged in succession such that each polaroid is turned through 30° with respect to the preceding one. The percentage of incident intensity that passes through the system will be |
| A. | 100% |
| B. | 0.5 |
| C. | Plane |
| D. | 0.12 |
| Answer» E. | |
| 71. |
A plane electromagnetic wave of wave intensity 6 W/m2 strikes a small mirror area 40 cm2, held perpendicular to the approaching wave. The momentum transferred by the wave to the mirror each second will be |
| A. | \[6.4\times {{10}^{-7}}kg-m/{{s}^{2}}\] |
| B. | \[4.8\times {{10}^{-8}}kg-m/{{s}^{2}}\] |
| C. | \[30{}^\circ \] |
| D. | \[1.6\times {{10}^{-10}}kg-m/{{s}^{2}}\] |
| Answer» E. | |
| 72. |
A point source of electromagnetic radiation has an average power output of 800 W. The maximum value of electric field at a distance 4.0 m from the source is |
| A. | 64.7 V/m |
| B. | 57.8 V/m |
| C. | \[3000\,\,{AA}\] |
| D. | 54.77 V/m |
| Answer» E. | |
| 73. |
A wave is propagating in a medium of electric dielectric constant 2 and relative magnetic permeability 50. The wave impedance of such a medium is |
| A. | 5 W |
| B. | 376.6 W |
| C. | \[\pi \] |
| D. | 3776 W |
| Answer» D. 3776 W | |
| 74. |
A laser beam can be focussed on an area equal to the square of its wavelength A He-Ne laser radiates energy at the rate of 1mW and its wavelength is 632.8 nm. The intensity of focussed beam will be |
| A. | \[1.5\times {{10}^{13}}\,W/{{m}^{2}}\] |
| B. | \[2.5\times {{10}^{9}}\,W/{{m}^{2}}\] |
| C. | \[a\sin \theta =\lambda \] |
| D. | None of these |
| Answer» C. \[a\sin \theta =\lambda \] | |
| 75. |
In an electromagnetic wave, the amplitude of electric field is 1 V/m. the frequency of wave is \[5\times {{10}^{14}}\,Hz\]. The wave is propagating along z-axis. The average energy density of electric field, in Joule/m3, will be |
| A. | \[1.1\times {{10}^{-11}}\] |
| B. | \[2.2\times {{10}^{-12}}\] |
| C. | Sound waves are mechanical waves |
| D. | \[4.4\times {{10}^{-14}}\] |
| Answer» C. Sound waves are mechanical waves | |
| 76. |
A long straight wire of resistance R, radius a and length l carries a constant current I. The Poynting vector for the wire will be |
| A. | \[\frac{IR}{2\pi al}\] |
| B. | \[\frac{I{{R}^{2}}}{al}\] |
| C. | \[a\sin \theta =\lambda \] |
| D. | \[\frac{{{I}^{2}}R}{2\pi al}\] |
| Answer» E. | |
| 77. |
Among the two interfering monochromatic sources A and B; A is ahead of B in phase by 66°. If the observation be taken from point P, such that PB ? PA = l/4. Then the phase difference between the waves from A and B reaching P is |
| A. | 156° |
| B. | 140° |
| C. | Sound waves are mechanical waves |
| D. | 126° |
| Answer» B. 140° | |
| 78. |
White light may be considered to be a mixture of waves with l ranging between\[3900\,\,{AA}\]and\[7800\,\,{AA}\]. An oil film of thickness\[10,000\,\,{AA}\]is examined normally by reflected light. If m = 1.4, then the film appears bright for |
| A. | \[4308\,\,{AA},\,\,5091\,\,{AA},\,\,6222\,\,{AA}\] |
| B. | \[4000\,\,{AA},\,\,5091\,\,{AA},\,\,5600\,\,{AA}\] |
| C. | q decreases |
| D. | \[4000\,\,{AA},\,\,4667\,\,{AA},\,\,5600\,\,{AA},\,\,7000\,\,{AA}\] |
| Answer» B. \[4000\,\,{AA},\,\,5091\,\,{AA},\,\,5600\,\,{AA}\] | |
| 79. |
In Young's double slit experiment, if the two slits are illuminated with separate sources, no interference pattern is observed because |
| A. | There will be no constant phase difference between the two waves |
| B. | The wavelengths are not equal |
| C. | 2.4 cm |
| D. | None of the above |
| Answer» B. The wavelengths are not equal | |
| 80. |
A wavefront presents one, two and three HPZ at points A, B and C respectively. If the ratio of consecutive amplitudes of HPZ is 4 : 3, then the ratio of resultant intensities at these point will be |
| A. | 169 : 16: 256 |
| B. | 256 : 16 : 169 |
| C. | \[{{n}^{2}}\] |
| D. | 256 : 196 : 16 |
| Answer» C. \[{{n}^{2}}\] | |
| 81. |
A circular disc is placed in front of a narrow source. When the point of observation is at a distance of 1 meter from the disc, then the disc covers first HPZ. The intensity at this point is I0. The intensity at a point distance 25 cm from the disc will be |
| A. | \[{{I}_{1}}=0.531{{I}_{0}}\] |
| B. | \[{{I}_{1}}=0.053{{I}_{0}}\] |
| C. | Fresnel |
| D. | \[{{I}_{1}}=5.03{{I}_{0}}\] |
| Answer» B. \[{{I}_{1}}=0.053{{I}_{0}}\] | |
| 82. |
Two coherent sources S1 and S2 are separated by a distance four times the wavelength l 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 |
| A. | 2 |
| B. | 3 |
| C. | \[0.34{}^\circ \] |
| D. | 5 |
| Answer» C. \[0.34{}^\circ \] | |
| 83. |
In a Young's double slit experiment, the slits are 2 mm apart and are illuminated with a mixture of two wavelength \[{{\lambda }_{0}}=750nm\] and \[\lambda =900nm\]. The minimum distance from the common central bright fringe on a screen 2m from the slits where a bright fringe from one interference pattern coincides with a bright fringe from the other is |
| A. | 1.5 mm |
| B. | 3 mm |
| C. | \[24\,m\] |
| D. | 6 mm |
| Answer» D. 6 mm | |
| 84. |
In Young's double slit experiment how many maxima?s can be obtained on a screen (including the central maximum) on both sides of the central fringe if \[\lambda =2000\,{AA}\] and \[d=7000\,{AA}\] |
| A. | 12 |
| B. | 7 |
| C. | \[\sqrt{6}\times {{10}^{-8}}m.\] |
| D. | 4 |
| Answer» C. \[\sqrt{6}\times {{10}^{-8}}m.\] | |
| 85. |
In Young?s double slit experiment, the two slits act as coherent sources of equal amplitude A and wavelengthl. In another experiment with the same set up the two slits are of equal amplitude A and wavelength l but are incoherent. The ratio of the intensity of light at the mid-point of the screen in the first case to that in the second case is [IIT-JEE 1986; RPMT 2002] |
| A. | 1 : 2 |
| B. | 2 : 1 |
| C. | 0 : 1 : 2 |
| D. | 1 : 1 |
| Answer» C. 0 : 1 : 2 | |
| 86. |
Four light waves are represented by (i) y = a1 sinw t (ii) \[y={{a}_{2}}\sin (\omega \,t+\varphi )\] (iii) \[y={{a}_{1}}\sin 2\omega \,t\] (iv) \[y={{a}_{2}}\sin 2(\,\omega \,t+\varphi )\] Interference fringes may be observed due to superposition of |
| A. | (i) and (ii) |
| B. | (i) and (iii) |
| C. | \[I=A+B\cos \frac{\varphi }{2}\] |
| D. | (iii) and (iv) |
| Answer» E. | |
| 87. |
In the figure is shown Young?s double slit experiment. Q is the position of the first bright fringe on the right side of O. P is the 11th fringe on the other side, as measured from Q. If the wavelength of the light used is \[6000\times {{10}^{-10}}m\], then \[{{S}_{1}}B\] will be equal to [CPMT 1986, 92] |
| A. | \[6\times {{10}^{-6}}m\] |
| B. | \[6.6\times {{10}^{-6}}m\] |
| C. | \[I(\theta )={{I}_{0}}/4\]for \[\theta ={{90}^{o}}\] |
| D. | \[3.144\times {{10}^{-7}}m\] |
| Answer» B. \[6.6\times {{10}^{-6}}m\] | |
| 88. |
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 \[{{10}^{-3}}m\], the wavelength of light used is [Roorkee 1992] |
| A. | \[6000\,\,{AA}\] |
| B. | \[5000\,\,{AA}\] |
| C. | Left handed rotation of 3° |
| D. | \[4500\,\,{AA}\] |
| Answer» B. \[5000\,\,{AA}\] | |
| 89. |
The periodic time of rotation of a certain star is 22 days and its radius is 7 ' 108 metres. If the wavelength of light emitted by its surface be\[4320\,\,{AA}\], the Doppler shift will be (1 day = 86400 sec) [MP PET 2001] |
| A. | \[0.033\,\,{AA}\] |
| B. | \[0.33\,\,{AA}\] |
| C. | 10?2 Joule |
| D. | \[33\,\,{AA}\] |
| Answer» B. \[0.33\,\,{AA}\] | |
| 90. |
The time period of rotation of the sun is 25 days and its radius is\[7\times {{10}^{8}}m\]. The Doppler shift for the light of wavelength\[6000\,\,{AA}\]emitted from the surface of the sun will be [MP PMT 1994] |
| A. | \[0.04\,\,{AA}\] |
| B. | \[0.40\,\,{AA}\] |
| C. | 0.3 |
| D. | \[40.0\,\,{AA}\] |
| Answer» B. \[0.40\,\,{AA}\] | |
| 91. |
When one of the slits of Young?s experiment is covered with a transparent sheet of thickness 4.8 mm, the central fringe shifts to a position originally occupied by the 30th bright fringe. What should be the thickness of the sheet if the central fringe has to shift to the position occupied by 20th bright fringe [KCET 2002] |
| A. | 3.8 mm |
| B. | 1.6 mm |
| C. | 56.72 V/m |
| D. | 3.2 mm |
| Answer» E. | |
| 92. |
Assertion : In everyday life the Doppler?s effect is observed readily for sound waves than light waves. Reason : Velocity of light is greater than that of sound. [AIIMS 1995] |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | 1883 W |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» C. 1883 W | |
| 93. |
Assertion : Nicol prism is used to produce and analyse plane polarised light. Reason : Nicol prism reduces the intensity of light to zero. |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | \[3.5\times {{10}^{17}}\,W/{{m}^{2}}\] |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» D. If the assertion and reason both are false. | |
| 94. |
Assertion : The unpolarised light and polarised light can be distinguished from each other by using polaroid. Reason : A polaroid is capable of producing plane polarised beams of light. |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | \[3.3\times {{10}^{-13}}\] |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion. | |
| 95. |
Assertion : The film which appears bright in reflected system will appear dark in the transmitted light and vice-versa. Reason : The conditions for film to appear bright or dark in reflected light are just reverse to those in the transmitted light. |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | \[\frac{{{I}^{2}}R}{al}\] |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion. | |
| 96. |
Assertion : No interference pattern is detected when two coherent sources are infinitely close to each other. Reason : The fringe width is inversely proportional to the distance between the two slits. |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | \[4667\,\,{AA},\,\,6222\,\,{AA},7000\,\,{AA}\] |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» C. \[4667\,\,{AA},\,\,6222\,\,{AA},7000\,\,{AA}\] | |