JEE Previous Year Question

In a Young's double slit experiment $15$ fringes are observed on a small portion of the screen when light of wavelength $500\text{nm}$ is used. Ten fringes are observed on the same section of the screen when another light source of wavelength $\lambda$ is used Then the value of $\lambda$is (in $\text{nm}$)

Topic: JEE PYQ

Answer: 750. Full step-by-step solution below.