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#photons

4 public questions tagged with this topic.

Photoelectric Effect - Work Function and Threshold

Which phenomenon provided evidence that light behaves as if it consists of quanta of energy?

**Photoelectric effect** demonstrates particle nature of light, photon energy E = h f, work function Φ = h f₀ minimum energy to eject electron, threshold frequency f₀ = Φ/h, threshold wavelength λ₀ = hc/Φ, hc=1240 eV·nm, maximum kinetic energy K_max = h f - Φ = e V₀, V₀ stopping potential, photocurrent proportional to intensity (number of photons) when f>f₀, saturation current depends on intensity, frequency determines K_max not current. The photoelectric effect demonstrated that light interacts with matter in discrete packets (photons), explained by Einstein’s quantum theory. Applying E = h f

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

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Photoelectric Effect - Work Function and Threshold

What does the photoelectric effect demonstrate about the nature of light?

**Classical wave theory fails** to explain instant emission, threshold existence, K_max dependence on frequency not intensity, saturation current dependence on intensity. Observations: K_max independent of intensity, exists threshold frequency, emission instantaneous, all explained by photon model E = h f, one photon ejects one electron, energy conservation h f = Φ + K_max. The photoelectric effect shows that light behaves as discrete packets of energy (photons), supporting its particle nature. Applying E = h f = h c/λ, p = h/λ, K_max = h f - Φ, Φ = h f₀ = h c/λ₀, λ = h/√(2 m e V) and f_max =

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

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PHYSICS

A photon has an energy of 4.14 × 10⁻¹⁹ J . What is its frequency? (Take h = 6.63 × 10⁻³⁴ J s )

Given: A photon has an energy of 4.14 × 10⁻¹⁹ J . What is its frequency? (Take h = 6.63 × 10⁻³⁴ J s ) These values define the system as per NCERT data. Formula: Energy of photon E = h v. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: v = E/h = frac4.14 × 10⁻¹⁹⁶.63 × 10⁻³⁴ approx 6.24 × 10¹⁴ Hz . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Oscillations and Waves, Topic: SHM, wave motion and superposition.

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