Two polaroids: I = I₀ cos²θ (Malus’ law)दो पोलेरॉइड: I = I₀ cos²θ (मैलस का नियम)Two polaroids: I = I₀ cos²θ (Malus’ law)

NCERT Fig 10.18 · Class 12 Physics · Chapter 10 · interactive diagram

Parts and what they mean

• Unpolarised light, intensity I (अध्रुवित प्रकाश, तीव्रता I) — From a lamp or the Sun: E vibrates in all directions ⊥ the beam.
• First polaroid P₁ (पहला पोलेरॉइड P₁) — Passes only the E-component along its pass-axis (the line drawn). Output intensity I/2, whatever the orientation of P₁.
• Linearly polarised light, I₀ = I/2 (रैखिकतः ध्रुवित प्रकाश, I₀ = I/2) — E now vibrates only along the pass-axis of P₁.
• Second polaroid P₂ (दूसरा पोलेरॉइड P₂) — Its pass-axis is at angle θ to that of P₁: only E cos θ gets through.
• Angle θ between pass-axes (पारित-अक्षों के बीच कोण θ) — θ = 0 → full I₀; θ = 90° (crossed) → zero.
• Transmitted light I₀ cos²θ (पारगमित प्रकाश I₀ cos²θ) — Amplitude E cos θ ⇒ intensity ∝ (E cos θ)² ⇒ I = I₀ cos²θ (Malus’ law).
• Malus’ law graph (मैलस नियम का ग्राफ़) — Two maxima and two minima as P₂ turns through 360° (shown: 0° to 180°).

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 10.18. Report a mistake