NEET Physics Ray Optics and Optical Instruments Questions Solved

NEET - 2016

A linear aperture whose width is 0.02 cm is placed immediately in front of a lens of focal length 60 cm. The aperture is illuminated normally by a parallel beam of wavelength 5×10-5 cm. The distance of the first dark band of the diffraction pattern from the dark band of the diffraction pattern from the centre of the screen is

(a) 0.10 cm             (b) 0.25 cm 

(c) 0.20 cm             (d) 0.15 cm

(d) Ist minima is formed at a distance 

                 Y=λDa

For the distance of the first dark band of the diffraction pattern from the centre of the screen is given by position of Ist minima.

 i.e.         Y=λDa

where, λ=wavelength of parallel beams

          D= focal length

          a= width of linear aperture.

y=5×10-50.60.02×10-2   given

Y=0.15 cm

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