JEE Main & Advanced Physics Wave Optics / तरंग प्रकाशिकी Question Bank

done Diffraction of Light Total Questions - 41

• question_answer1)
   A slit of width\[a\]is illuminated by white light. For red light\[(\lambda =6500\,\,{AA})\], the first minima is obtained at\[\theta ={{30}^{o}}.\] Then the value of a will be  [MP PMT 1987; CPMT 2002]
  A)
  \[3250\,\,{AA}\] done clear
  B)
  \[6.5\times {{10}^{-4}}mm\] done clear
  C)
  1.24 microns                          done clear
  D)
  \[2.6\times {{10}^{-4}}cm\] done clear
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• question_answer2)
  The light of wavelength\[6328\,\,{AA}\]is incident on a slit of width 0.2 mm perpendicularly, the angular width of central maxima will be                                   [MP PMT 1987; Pb. PMT 2002]
  A)
  \[{{0.36}^{o}}\]                    done clear
  B)
  \[{{0.18}^{o}}\] done clear
  C)
  \[{{0.72}^{o}}\]                    done clear
  D)
  \[{{0.09}^{o}}\] done clear
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• question_answer3)
  The bending of beam of light around corners of obstacles is called            [NCERT 1990; AFMC 1995; RPET 1997; RPMT 1997; CPMT 1999; JIPMER 2000]
  A)
             Reflection                              done clear
  B)
             Diffraction done clear
  C)
             Refraction                              done clear
  D)
             Interference done clear
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• question_answer4)
  The penetration of light into the region of geometrical shadow is called                                 [CPMT 1999; JIPMER 2000]
  A)
             Polarization                           done clear
  B)
             Interference done clear
  C)
             Diffraction                              done clear
  D)
             Refraction done clear
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• question_answer5)
  A slit of size 0.15 cm is placed at 2.1 m from a screen. On illuminated it by a light of wavelength 5 ´ 10?5 cm. The width of central maxima will be                         [RPMT 1999]
  A)
             70 mm                                     done clear
  B)
             0.14 mm done clear
  C)
             1.4 mm                                    done clear
  D)
             0.14 cm done clear
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• question_answer6)
  A diffraction is obtained by using a beam of red light. What will happen if the red light is replaced by the blue light [KCET 2000; BHU 2001]
  A)
             Bands will narrower and crowd full together done clear
  B)
             Bands become broader and further apart done clear
  C)
             No change will take place done clear
  D)
             Bands disappear done clear
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• question_answer7)
  What will be the angle of diffracting for the first minimum due to Fraunhoffer diffraction with sources of light of wave length 550 nm and slit of width 0.55 mm                          [Pb. PMT 2001]
  A)
             0.001 rad                                done clear
  B)
             0.01 rad done clear
  C)
             1 rad                                         done clear
  D)
             0.1 rad done clear
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• question_answer8)
  Angular  width (b) of central maximum of a diffraction pattern on a single slit does not depend upon [DCE 2000; 01]
  A)
             Distance between slit and source done clear
  B)
             Wavelength of light used done clear
  C)
             Width of the slit done clear
  D)
             Frequency of light used done clear
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• question_answer9)
  A single slit of width 0.20 mm is illuminated with light of wavelength 500 nm. The observing screen is placed 80 cm from the slit. The width of the central bright fringe will be   [AMU (Med.) 2002]
  A)
             1 mm                                        done clear
  B)
             2 mm  done clear
  C)
             4 mm                                        done clear
  D)
             5 mm done clear
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• question_answer10)
  Yellow light is used in single slit diffraction experiment with slit width 0.6 mm. If yellow light is replaced by X-rays then the pattern will reveal  [IIT-JEE  (Screening) 1999; MP PMT 2002; KCET 2003]
  A)
             That the central maxima is narrower done clear
  B)
             No diffraction pattern done clear
  C)
             More number of fringes done clear
  D)
             Less number of fringes done clear
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• question_answer11)
  Which statement is correct for a zone plate and a lens  [RPMT 2002]
  A)
             Zone plate has multi focii whereas lens has one done clear
  B)
             Zone plate has one focus whereas lens has multiple focii done clear
  C)
             Both are correct done clear
  D)
             Zone plate has one focus whereas a lens has infinite done clear
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• question_answer12)
  In Fresnel diffraction, if the distance between the disc and the screen is decreased, the intensity of central bright spot will                                                                                             [RPMT 2002]
  A)
             Increase                                  done clear
  B)
             Decrease done clear
  C)
             Remain constant                 done clear
  D)
             None of these done clear
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• question_answer13)
  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)
             \[6\,mm\]                              done clear
  B)
             \[12\,mm\] done clear
  C)
             \[3\,mm\]                              done clear
  D)
             \[9\,mm\] done clear
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• question_answer14)
  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)
  \[36\times {{10}^{-8}}m.\]      done clear
  B)
  \[6\times {{10}^{-8}}m.\] done clear
  C)
  \[\sqrt{6}\times {{10}^{-8}}m.\]                                       done clear
  D)
  \[6\times {{10}^{-4}}m.\] done clear
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• question_answer15)
  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)
  \[9\,m\]                                  done clear
  B)
  \[12\,m\] done clear
  C)
  \[24\,m\]                                done clear
  D)
  \[36\,m\] done clear
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• question_answer16)
  Red light is generally used to observe diffraction pattern from single slit. If blue light is used instead of red light, then diffraction pattern [RPMT 2001; BCECE 2005; CPMT 2005]
  A)
             Will be clearer                      done clear
  B)
             Will contract done clear
  C)
             Will expanded                      done clear
  D)
             Will not be visualized done clear
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• question_answer17)
  In the experiment of diffraction at a single slit, if the slit width is decreased, the width of the central maximum [KCET 2001]
  A)
             Increases in both Fresnel and Fraunhofer diffraction done clear
  B)
             Decreases both in Fresnal and Fraunhofer diffraction done clear
  C)
             Increases in Fresnel diffraction but decreases in Fraunhofer diffraction done clear
  D)
             Decreases in Fresnel diffraction but increases is Fraunofer diffraction. done clear
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• question_answer18)
  Conditions of diffraction is                                          [RPET 2001]
  A)
             \[\frac{a}{\lambda }=1\]  done clear
  B)
             \[\frac{a}{\lambda }>>1\] done clear
  C)
             \[\frac{a}{\lambda }<<1\]       done clear
  D)
             None of these done clear
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• question_answer19)
  Light of wavelength \[589.3\,nm\] is incident normally on the slit of width \[0.1\,mm.\] What will be the angular width of the central diffraction maximum at a distance of \[1\,m\] from the slit                                                   [BHU (Med.) 1999]
  A)
             \[0.68{}^\circ \]                    done clear
  B)
             \[1.02{}^\circ \] done clear
  C)
             \[0.34{}^\circ \]                    done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer20)
  The phenomenon of diffraction of light was discovered by [KCET 2000]
  A)
             Hygens                                    done clear
  B)
             Newton done clear
  C)
             Fresnel                                    done clear
  D)
             Grimaldi done clear
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• question_answer21)
  The radius \[r\] of half period zone is proportional to [RPMT 1998, 2002]
  A)
             \[\sqrt{n}\]                            done clear
  B)
             \[\frac{1}{\sqrt{n}}\] done clear
  C)
             \[{{n}^{2}}\]                          done clear
  D)
             \[\frac{1}{n}\] done clear
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• question_answer22)
  In a diffraction pattern by a wire, on increasing diameter of wire, fringe width                                    [RPMT 1998]
  A)
             Decreases done clear
  B)
             Increases done clear
  C)
             Remains unchanged done clear
  D)
             Increasing or decreasing will depend on wavelength done clear
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• question_answer23)
  What will be the angular width of central maxima in Fraunhoffer diffraction when light of wavelength \[6000\,{AA}\] is used and slit width is \[12\times {{10}^{-5}}cm.\] [RPMT 2004]
  A)
  2 rad                                         done clear
  B)
  3 rad done clear
  C)
  1 rad                                         done clear
  D)
  8 rad done clear
  View Solution play_arrow

• question_answer24)
  When a compact disc is illuminated by a source of white light. Coloured 'lanes' are observed. This is due to [DCE 2003; AIIMS 2004]
  A)
             Dispersion                              done clear
  B)
             Diffraction done clear
  C)
             Interference                         done clear
  D)
             Refraction done clear
  View Solution play_arrow

• question_answer25)
  The diffraction effect can be observed in      [J & K CET 2004]
  A)
             Only sound waves done clear
  B)
             Only light waves done clear
  C)
             Only ultrasonic waves  done clear
  D)
             Sound as well as light waves done clear
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• question_answer26)
  If we observe the single slit Fraunhofer diffraction with wavelength l and slit width e, the width of the central maxima is 2q. On decreasing the slit width for the same l  [UPSEAT 2004]
  A)
             q increases done clear
  B)
             q remains unchanged  done clear
  C)
             q decreases done clear
  D)
             q increases or decreases depending on the intensity of light done clear
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• question_answer27)
  When light is incident on a diffraction grating the zero order principal maximum will be                  [KCET 2004]
  A)
             One of the component colours done clear
  B)
             Absent done clear
  C)
             Spectrum of the colours done clear
  D)
             White done clear
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• question_answer28)
  A beam of light of wavelength 600 nm from a distant 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   [IIT-JEE 1994; KCET 2004]
  A)
             1.2 mm                                    done clear
  B)
             1.2 cm done clear
  C)
             2.4 cm                                      done clear
  D)
             2.4 mm done clear
  View Solution play_arrow

• question_answer29)
  In order to see diffraction the thickness of the film is [J&K CEE 2001]
  A)
  \[100\,\,{AA}\]                   done clear
  B)
  \[10,000\,\,{AA}\] done clear
  C)
  1 mm                                        done clear
  D)
  1 cm done clear
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• question_answer30)
  Diffraction effects are easier to notice in the case of sound waves than in the case of light waves because [RPET 1978; KCET 1994, 2000]
  A)
             Sound waves are longitudinal done clear
  B)
             Sound is perceived by the ear done clear
  C)
             Sound waves are mechanical waves done clear
  D)
             Sound waves are of longer wavelength done clear
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• question_answer31)
  Direction of the first secondary maximum in the Fraunhofer diffraction pattern at a single slit is given by (a is the width of the slit)                                                       [KCET 1999]
  A)
             \[a\sin \theta =\frac{\lambda }{2}\]                               done clear
  B)
             \[a\cos \theta =\frac{3\lambda }{2}\] done clear
  C)
             \[a\sin \theta =\lambda \]      done clear
  D)
             \[a\sin \theta =\frac{3\lambda }{2}\] done clear
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• question_answer32)
  A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of incident beam. At the first maximum of the diffraction pattern the phase difference between the rays coming from the edges of the slit is                                                              [IIT?JEE 1995, 98]
  A)
             0     done clear
  B)
             \[\frac{\pi }{2}\] done clear
  C)
             \[\pi \]                                     done clear
  D)
             \[2\pi \] done clear
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• question_answer33)
  Diffraction and interference of light suggest [CPMT 1995; RPMT 1998]
  A)
             Nature of light is electro-magnetic done clear
  B)
             Wave nature done clear
  C)
             Nature is quantum done clear
  D)
             Nature of light is transverse done clear
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• question_answer34)
  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)
  \[6000\,\,{AA}\]                done clear
  B)
  \[5000\,\,{AA}\] done clear
  C)
  \[3000\,\,{AA}\]                done clear
  D)
  \[1500\,\,{AA}\] done clear
  View Solution play_arrow

• question_answer35)
  A parallel beam of monochromatic light of wavelength\[5000\,\,{AA}\]is incident normally on a single narrow slit of width 0.001 mm. The light is focused by a convex lens on a screen placed on the focal plane. The first minimum will be formed for the angle of diffraction equal to      [CBSE PMT 1993]
  A)
  \[0{}^\circ \]  done clear
  B)
  \[15{}^\circ \] done clear
  C)
  \[30{}^\circ \] done clear
  D)
  \[60{}^\circ \] done clear
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• question_answer36)
  The condition for observing Fraunhofer diffraction from a single slit is that the light wavefront incident on the slit should be                                                                       [MP PMT 1987]
  A)
             Spherical                                 done clear
  B)
             Cylindrical done clear
  C)
             Plane done clear
  D)
             Elliptical done clear
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• question_answer37)
  To observe diffraction the size of an obstacle   [CPMT 1982]
  A)
             Should be of the same order as wavelength done clear
  B)
             Should be much larger than the wavelength done clear
  C)
             Have no relation to wavelength done clear
  D)
             Should be exactly \[\frac{\lambda }{2}\] done clear
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• question_answer38)
  In the far field diffraction pattern of a single slit under polychromatic illumination, the first minimum with the wavelength \[{{\lambda }_{1}}\] is found to be coincident with the third maximum at \[{{\lambda }_{2}}\]. So
  A)
             \[3{{\lambda }_{1}}=0.3{{\lambda }_{2}}\]                  done clear
  B)
             \[3{{\lambda }_{1}}={{\lambda }_{2}}\] done clear
  C)
             \[{{\lambda }_{1}}=3.5{{\lambda }_{2}}\]                     done clear
  D)
             \[0.3{{\lambda }_{1}}=3{{\lambda }_{2}}\] done clear
  View Solution play_arrow

• question_answer39)
  Light of wavelength\[\lambda =5000\,\,{AA}\]falls normally on a narrow slit. A screen placed at a distance of 1 m from the slit and perpendicular to the direction of light. The first minima of the diffraction pattern is situated at 5 mm from the centre of central maximum. The width of the slit is
  A)
  0.1 mm                                    done clear
  B)
  1.0 mm done clear
  C)
  0.5 mm                                    done clear
  D)
  0.2 mm done clear
  View Solution play_arrow

• question_answer40)
  The width of the nth HPZ will be
  A)
             \[\sqrt{nb\lambda }\]       done clear
  B)
             \[\sqrt{b\lambda }\,[\sqrt{n}-\sqrt{n-1}]\] done clear
  C)
             \[(\sqrt{n}\,-\,\sqrt{n-1})\]    done clear
  D)
             \[\frac{\sqrt{b\lambda }}{[\sqrt{n}\,-\sqrt{n-1}]}\] done clear
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• question_answer41)
  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                                              [KCET 2005]
  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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