Question

The width of a slit is 0.012 mm. Monochromatic light is incident on it. The angular position of first bright line is 5.2${}^o$. The wavelength of incident light is :(given $sin{5.2}^0=0.0906$)

• A. 6040 $\stackrel{o}{A}$
• B. 4026 $\stackrel{o}{A}$
• C. 5890 $\stackrel{o}{A}$
• D. 7248 $\stackrel{o}{A}$

Answer 1

The correct option is D 7248 $\stackrel{o}{A}$

It is one of a Fraunhoffer's diffraction from single slit. So for bright fringe where a is the width of slit.
$asin$ $\theta$ = $(2n+1)$ $\frac{\lambda }{2}$
$\lambda$ = $\frac{2asin\theta }{2n+1}$ = $\frac{2\times 1.2\times {10}^{-5}\times 0.0906}{2\times 1+1}$
=$7248$ $\times$ $10$ ${}^{-10}$ m =$7248$ $\stackrel{o}{A}$