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#photon wavelength

10 public questions tagged with this topic.

Photoelectric Effect - Work Function and Threshold

Light of wavelength \( 300 \, \text{nm} \) produces a stopping potential of \( 1.5 \, \text{V} \). What is the work func

**Work function** Φ minimum energy to escape, for Φ=2.2 eV λ₀=1240/2.2=563.6 nm, Φ=3.0 eV threshold frequency f₀=Φ/h=3×1.6×10⁻¹⁹/6.63×10⁻³⁴=7.24×10¹⁴ Hz, stopping potential V₀ = (h f - Φ)/e, for 0.7 V K_max=0.7 eV, for 1.5 V K_max=1.5 eV, intensity increase increases photocurrent not K_max, frequency below threshold no emission regardless of intensity. E = (h c/λ) = (1240/300) ≈ 4.13 eV . Kₘₐₓ = e V₀ = 1.5 eV . Φ₀ = E - Kₘₐₓ = 4.13 - 1.5 = 2.63 eV . Applying E = h f = h c/λ, p = h/λ, K_max = h f - Φ, Φ = h f₀ = h c/λ₀,

Ref: NCERT > Physics Book > Dual Nature of Matter > Photoelectric Effect - Work Function and Threshold

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Atomic Models - Rutherford, Thomson and Bohr

What is the wavelength of a photon emitted when an electron drops from \( n = 4 \) to \( n = 3 \) in a hydrogen atom? (U

**Thomson's plum pudding model** positive charge uniformly distributed in sphere with electrons embedded, positive charge spread, fails to explain large angle scattering observed. Bohr's model introduces stationary orbits with quantized angular momentum L = n h/2π, physical basis de Broglie standing wave condition 2πr = n λ, circumference fits n wavelengths, explains line spectrum. Δ E = 0.66 eV = 1.056 × 10⁻¹⁹ J . λ = (hc/Δ E) = (6.6 × 10⁻³⁴ × 3 × 10⁸/1.056 × 10⁻¹⁹) ≈ 1.875 × 10⁻⁶ m . Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm

Ref: NCERT > Physics Book > Atoms and Nuclei > Atomic Models - Rutherford, Thomson and Bohr

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Atomic Models - Rutherford, Thomson and Bohr

What is the wavelength of the photon emitted when an electron drops from \( n = 2 \) to \( n = 1 \) in a hydrogen atom?

**Bohr's stationary orbits** defined by angular momentum quantization L = n ħ, ħ = h/2π, n=1 ground state, electron in these orbits does not radiate despite acceleration, contrary to classical EM theory which predicts atom collapse due to energy loss via radiation, Bohr postulates to explain observed stability and discrete spectra. Δ E = 10.2 eV = 1.632 × 10⁻¹⁸ J . λ = (hc/Δ E) = (6.6 × 10⁻³⁴ × 3 × 10⁸/1.632 × 10⁻¹⁸) ≈ 1.21 × 10⁻⁷ m . Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm c² and 1

Ref: NCERT > Physics Book > Atoms and Nuclei > Atomic Models - Rutherford, Thomson and Bohr

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Developments Leading to Bohr Model - Electromagnetic Radiation and Spectrum

An electron in He⁺ transitions from n = 3 to n = 1. What is the wavelength of the emitted photon in nm? (RH = 1.097 × 10

For He⁺ (Z=2), wavenumber ν̄ = Z² RH (1/n₁² - 1/n₂²) = 4 × 1.097×10⁷ (1/1² - 1/3²) ≈ 3.901×10⁷ m⁻¹. λ = 1/ν̄ ≈ 2.563×10⁻⁸ m = 25.63 nm.

Ref: NCERT Class 11 Chemistry > Chapter 2: Structure of Atom > Topic: Developments Leading to Bohr Model - Electromagnetic Radiation and Spectrum

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