In YDSE, the two slits are separated by 0.1 mm and they are 0.5 m from the screen. The wavelength of light used is 5000 A°. What is the distance between 7th maximum and 11th minimum on the screen?

Q: In YDSE, the two slits are separated by 0.1 mm and they are 0.5 m from the screen. The wavelength of light used is 5000 A°. What is the distance between 7th maximum and 11th minimum on the screen?

Sol: Here, d = 0.1 mm = 10^-4 m,

D = 0.5 m, λ = 5000 A° = 5.0 × 10^-7 m

∆y = (y₁₁)_dark -(y₇)_bright

$\large \Delta y = \frac{(2 \times 11 -1)\lambda D}{2 d} – \frac{7 \lambda D}{d} $

$\large \Delta y = \frac{7 \lambda D}{2 d} $

$\large \Delta y = \frac{7 \times 5 \times 10^{-3}}{2 \times 10^{-4}} $

= 8. 75 × 10^-3 m

= 8. 75 mm.