Bohr’s third postulate: emission and absorption of a photonबोर का तृतीय अभिगृहीत: फ़ोटॉन का उत्सर्जन और अवशोषणBohr’s third postulate: emission and absorption of a photon

NCERT §12.4, §12.5 · Class 12 Physics · Chapter 12 · interactive diagram

Parts and what they mean

• Higher energy level E₂ (उच्च ऊर्जा स्तर E₂) — A stationary state with more energy (larger n).
• Lower energy level E₁ (निम्न ऊर्जा स्तर E₁) — A stationary state with less energy (smaller n).
• Electron drops E₂ → E₁ (इलेक्ट्रॉन E₂ → E₁ गिरता है) — The atom loses energy E₂ − E₁ …
• Emitted photon (उत्सर्जित फ़ोटॉन) — … carried away by one photon: hν = E₂ − E₁. This gives a bright emission line.
• Absorbed photon (अवशोषित फ़ोटॉन) — Only a photon with exactly hν = E₂ − E₁ is absorbed. Missing photons appear as a dark absorption line.
• Electron rises E₁ → E₂ (इलेक्ट्रॉन E₁ → E₂ उठता है) — The atom goes to a higher stationary state (larger n): E₁ + hν = E₂.

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