What happens to the kinetic energy of the emitted electrons when the light is incident on a metal surface?

The correct answer is It varies with the frequency of light.

Key Points

• In the photoelectric effect, the kinetic energy of emitted electrons depends directly on the frequency of the incident light.
• The relationship is governed by Einstein's photoelectric equation: KE = hf - Φ, where h is Planck's constant, f is the frequency of light, and Φ is the work function of the metal.
• If the frequency of light increases beyond the threshold frequency, the excess energy is imparted to the electrons as kinetic energy.
• Light intensity affects the number of electrons emitted, but not their kinetic energy, which is solely frequency-dependent.
• Below the threshold frequency, no electrons are emitted, regardless of the intensity of the light.

Additional Information

• Photoelectric Effect:
  • It is the phenomenon of electrons being emitted from a metal surface when light of sufficient frequency strikes it.
  • The effect was first observed by Wilhelm Hallwachs in 1887 and later explained by Albert Einstein in 1905.
  • Einstein received the Nobel Prize in Physics in 1921 for his explanation of the photoelectric effect.
• Threshold Frequency:
  • The minimum frequency of light required to eject electrons from a metal surface is called the threshold frequency.
  • It is specific to each metal and is related to the metal's work function.
• Work Function:
  • The work function is the minimum energy required to eject an electron from the surface of a metal.
  • It is measured in electron volts (eV) and varies for different metals.
• Planck's Constant:
  • It is a fundamental constant denoted by h, with a value of approximately 6.626 × 10⁻³⁴ Js.
  • Planck's constant links the energy of a photon to its frequency through the equation E = hf.
• Applications of Photoelectric Effect:
  • The phenomenon is utilized in devices like photocells, which convert light energy into electrical energy.
  • It plays a key role in technologies such as solar panels, light sensors, and imaging devices.