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JEE MAIN Physics QUESTION #990
Question 1
Assertion (A): In Young's double slit experiment, fringes produced by red light are wider compared to blue light. Reason (R): Fringe width is directly proportional to the wavelength of light. Choose the correct option:
  • Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
  • (A) is true but (R) is false
  • Both (A) and (R) are true and (R) is the correct explanation of (A)
  • (A) is false but (R) is true✔️
Correct Answer Explanation
Fringe width \(\beta = \frac{\lambda D}{d}\). Since \(\lambda_{red} > \lambda_{blue}\), red fringes are wider, not closer. The assertion in the paper states red fringes are 'closer' which is false. But (R) is true. Hence (A) is false but (R) is true.