Question

Change in fringe width produced due to change in wavelength is

• A. $-0.57\times {10}^{-4}m$
• B. $-0.47\times {10}^{-4}m$
• C. $-0.37\times {10}^{-4}m$
• D. $-0.27\times {10}^{-4}m$

Answer 1

The correct option is A $-0.57\times {10}^{-4}m$

$5\frac{D{\lambda }_{red}}{d}={10}^{-3}m$

$\beta =\frac{D\lambda }{d}$

$⟹\Delta \beta =\frac{D\Delta \lambda }{d}$

$=\left(\frac{{10}^{-3}}{5{\lambda }_{red}}\right)(5\times {10}^{-7}-7\times {10}^{-7})=-0.57\times {10}^{-4}m$