Question

Direction of the second maximum in the fraunhofer pattern at a single slit is given by ( a is the width of the slit)

• A. $asin\theta =\frac{\lambda }{2}$
• B. $acos\theta =\frac{3\lambda }{2}$
• C. $asin\theta =\lambda$
• D. $asin\theta =\frac{3\lambda }{2}$

Answer 1

Answer: (A)

$asin\theta =\frac{\lambda }{2}$

Given,

Width of slit is $a$

$n=0$

For nth secondary maxima path difference

$asin\theta =(2n+1)\frac{\lambda }{2}$

putting $n=0$ in above equation

$asin\theta =(2\times 0+1)\frac{\lambda }{2}=(0+1)\frac{\lambda }{2}=\frac{\lambda }{2}$

Correct option is A