Question

Light of wavelength 575 nm passes through a double-slit and the third order bright fringe is seen at an angle of 6.5^degree away from the central fringe. What is the separation between the double slits? a) 5.0 mu m b) 10 mu m c) 15 mu m d) 20 mu m e) 25 mu m

Answer 1

Answer:

The correct option is C

Explanation:

From the question we are told that

   The wavelength is  $\lambda = 575 *10^{-9} \ m$

    The  angle is  $\theta = 6.5^o$

    The order of maxima  is  n =  3

Generally for  constructive interference

       $dsin \theta = n * \lambda$

=>   $d = \frac{n * \lambda }{ sin \theta }$

=>   $d = \frac{3 * 575 *10^{-9} }{ sin 6.5 }$

=>   $d = 15.24 *10^{-6} \ m$

=>  $d = 15 \mu m$