Study Guides/Physics/Threshold Frequency
Study Guide · Physics

What is Threshold Frequency in Physics?

The concept of Threshold Frequency is central to understanding the Photoelectric Effect, a topic in Class 12 Physics that helped Einstein win the Nobel Prize.

Question (Click to Flip)

What is threshold frequency?

Answer

Threshold frequency (ν₀) is the minimum frequency of incident light required to eject an electron from a metal surface. Below this frequency, no photoelectric emission occurs regardless of the light's intensity.

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Key Facts

Symbol: ν₀ (nu-naught).

Definition: Minimum frequency of light that causes photoelectric emission.

Formula: φ = hν₀.

Key Point: Intensity does NOT matter below threshold frequency — frequency is the deciding factor.

Definition of Threshold Frequency

Threshold Frequency (ν₀) is defined as the minimum frequency of incident light required to eject electrons from the surface of a metal.

  • If the frequency of light hitting the metal is below ν₀, no electrons will be emitted, no matter how intense (bright) the light is.
  • If the frequency is equal to or greater than ν₀, electrons are immediately emitted.

Relationship with Work Function

The threshold frequency is directly related to the Work Function (φ) of the metal — the minimum energy needed to release one electron from the metal surface.

Formula: φ = hν₀

Where:

  • φ = Work Function (in Joules or eV)
  • h = Planck's constant (6.626 × 10⁻³⁴ J·s)
  • ν₀ = Threshold Frequency

Each metal has its own unique threshold frequency. Metals like Caesium and Potassium have low threshold frequencies (making them ideal for solar cells).

Questions and Answers

What is threshold frequency?+

Threshold frequency (ν₀) is the minimum frequency of incident light required to eject an electron from a metal surface. Below this frequency, no photoelectric emission occurs regardless of the light's intensity.

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