The radius of the nth Bohr orbit in hydrogen atom is proportional to:
A. n
B. n²
C. 1/n²
D. 1/n
Answer: Option B
Solution (By JKSSB Mock Tests)
Bohr model: radius r_n = (4πε₀ħ²n²)/(m_e e²) = n² a₀, where a₀ is Bohr radius (≈0.529 Å). Thus r_n ∝ n². Energy E_n ∝ -1/n². Memory tip: 'Bohr radius: r ∝ n²; energy: E ∝ -1/n²'. This atomic physics formula is frequently tested in competitive exams. Always recall that n is principal quantum number; higher n means larger orbit, less tightly bound electron. This problem assesses understanding of quantization in early quantum theory.
Explanation:
Watt is unit of power (J/s). Kilowatt-hour is energy (power × time). Joule is SI unit of energy. Electron volt is energy unit (1.6×10⁻¹⁹ J). Remember: power = energy/time. So watt is not energy.
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