Q. Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : In Young's double slit experiment, the fringes produced by red light are closer as compared to those produced by blue light. Reason (R): The fringe width is directly proportional to the wavelength of light. In the light of the above statements, choose the correct answer from the options given below :
A) Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
B) (A) is true but (R) is false
C) Both (A) and (R) are true and (R) is the correct explanation of (A)
D) (A) is false but (R) is true
Explanation
[Solution by Dr. Abubacker] Fringe width $\beta=\frac{\lambda D}d\propto\lambda$, so (R) is true. Red light has a longer wavelength than blue, so its fringes are wider, not closer. (A) is false. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.