Physics · Einstein's photoelectric equation, particle nature of light

Light of two different frequencies whose protons have energies and respectively,

Light of two different frequencies whose protons have energies \( 1 e V \) and \( 2.5 e V \) respectively, successively illuminate a metallic surface whose work function is \( 0.5 e V . \) Ratio of maximum speeds of emitted electrons will be

  • A. 1: 5
  • B. 1: 4
  • C. 1: 2
  • D. 1: 1

Step-by-step solution

Using Einstein's photoelectric equation: K_max = hν - φ. For first photon, K1 = 1 eV - 0.5 eV = 0.5 eV. For second, K2 = 2.5 eV - 0.5 eV = 2.0 eV. Since K = (1/2)mv^2, v ∝ √K. Thus v1/v2 = √(0.5/2.0) = √0.25 = 0.5 = 1:2.
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