Questions and Solutions Part 1

1. In Young's double slit experiment the light emited from source has l = 6.5 × 10–7 m and the distance between the two slits is 1 mm. Distance between the screen and slit is 1 metre. Distance between third dark and fifth birth fringe will be 
    (a) 3.2 mm    (b) 1.63 mm    (c) 0.585 mm        (d) 2.31 mm

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2. Light is incident normally on a diffraction grating through which first order diffraction is seen at 32o. The second order diffraction will be seen at 
    (a) 84       (b) 48o
    (c) 64o         (d) None of these

515_solution 2.jpg

Which is not possible. Hence there is no second order diffraction.

 

3.    In Young's double slit experiment, if the widths of the slit are in the ratio 4:9, ratio of intensity of maxima to intensity of minima will be 
    (a) 25:1    (b) 9:4    (c) 3:2        (d) 81:16

Solution-    (a)
As ratio of slit widths = Ratio of intensities

1243_answers wave optics.jpg

 

4.    A light source approaches the observer with velocity 0.5 cm. Doppler shift for light of wavelength 550 Å is 
    (a) 616 Å    (b) 1833 Å     (c) 5500 Å        (d) 6160 Å

1678_answers wave optics 1.jpg

5.    Angular width of a central max. is 30o when the slit is illuminated by light of wavelength 6000 Å. Then width of the slit will be approx. 
    (a) 12 × 10–6 m    (b) 12 × 10–7 m    (c) 12 × 10–8 m    (d) 12 × 10–9 m

 

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6.    Light of wavelength 6000 12 × 10–6 m is incident on a single slit. First minimum is obtained at a distance of 0.4 cm from the centre. If width of the slit is 0.3 mm, then distance between slit and screen will be 
    (a) 1.0 m    (b) 1.5 m    (c) 2.0 m        (d) 2.3 m

1214_optics relative velocity.jpg

8.    Doppler shift for the light of wavelength 6000 Å emitted from the sun is 0.04 Å. If radius of the sun is 7 × 108 m then time period of rotation of the sun will be   
    (a) 30 days    (b) 365 days    (c) 24 hours        (d) 25 days.

750_wave optics examples.jpg                               

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10.    If light with wavelength 0.50 mm falls on a slit of width 10 mm and at an angle =  30o to its normal. Then angular position of first minima located on right sides of the central Fraunhoffer's diffraction will be at  
    (a) 33.4o         (b) 26.8o
    (c) 39.8o        (d) None of these

796_fraunhoffer question.jpg

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