Q 12-10-128JEE MainJEE Main 2020 (2 Sep, Shift 2)Easy
In a Young's double slit experiment, $16$ fringes are observed in a certain segment of the screen when light of wavelength $700\ \text{nm}$ is used. If the wavelength of light is changed to $400\ \text{nm}$, the number of fringes observed in the same segment of the screen would be:
Answer: (D) $28$
Fringe width $\beta \propto \lambda$, so the number of fringes in a fixed length is $\propto 1/\lambda$:
$$N_2 = 16\times\frac{700}{400} = 28$$
Solution by Sreeraj P, M.Sc Physics