Question

Assertion :In Young's double slit experiment if wavelength of incident monochromatic light is just doubled, number of bright fringe on the screen will increase Reason: Maximum number of bright lunge on the screen is inversely proportional to the wavelength of light used

• A. Assertion is incorrect and Reason are correct
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. ssertion is correct but Reason is incorrect;Reason is not correct explanation for Assertion
• D. Both Assertion is correct and Reason are incorrect

Answer 1

The correct option is A Assertion is incorrect and Reason are correct

Fringe width of a YDSE interference pattern is given by $\beta =\frac{D\lambda }{d}$.

Number of bright fringes possible on a screen of finite width 'S' is $\frac{S}{\beta }$

Hence, number of bright fringes obtained$\propto \frac{1}{\lambda }$

Hence as $\lambda$ doubles, number of bright fringes obtained halves.