RE-NEET 2024 Physics Young's Double Slit Experiment MCQ Question

Topic: Young’s Double Slit Experiment Difficulty: 🟡 Medium

✅ Ans: D — $4\times10^{-4}\,m$

Fringe separation:

$$\beta=\frac{\lambda D}{d}$$

(MedicNEET)

Given:

$$\lambda=600\times10^{-9}m,\quad D=1m,\quad d=1.5mm=1.5\times10^{-3}m$$ $$\beta=\frac{600\times10^{-9}\times1}{1.5\times10^{-3}}$$ $$\boxed{\beta=4\times10^{-4}m}$$

❌ Why other options are wrong?

They result from incorrect conversion of mm to m or incorrect substitution.

📌 NCERT: $\beta=\frac{\lambda D}{d}$

🧠 NEET Trick: Fringe width = λD/d → λ and D on top, d below.