Light of frequency 7 . 21 × 10 14 Hz is incident on a metal surface. Electrons with a maximum speed of 6 . 0 × 10 5 m s are ejected from the surface. What is the threshold frequency for photoemission of electrons?

The frequency of the incident light is, ν = 7 . 21 × 10 14 Hz The maximum speed of the electron is, v e = 6.0 × 1 0 5 m s - 1 The kinetic energy is: 1 2 m v e 2 = h ν - ν ∘ ........................... 1 Here, ν ∘ is threshold frequency and h = 6.626 × 1 0 - 34 J s is the Planck’s constant. The mass of the electron is, m = 9.1 × 1 0 - 31 kg From equation 1 ν ∘ = ν − m v e 2 2 h ........................... 2 By substituting value in this ν ∘ = 7 .21 × 10 14 Hz − 9 .1 × 10 − 31 kg 6 .0 × 10 5 m s - 1 2 2 6 .626 × 10 − 34 J s = 4 . 57 × 10 14 Hz Hence, the threshold frequency for the photoemission of electrons is 4 . 57 × 10 14 Hz .

Light of frequency 7 . 21 × 10 14 Hz is incident on a metal surface. Electrons with a maximum speed of 6 . 0 × 10 5 m s are ejected from the surface. What is the threshold frequency for photoemission of electrons?

The frequency of the incident light is, ν = 7 . 21 × 10 14 Hz The maximum speed of the electron is, v e = 6.0 × 1 0 5 m s - 1 The kinetic energy is: 1 2 m v e 2 = h ν - ν ∘ ........................... 1 Here, ν ∘ is threshold frequency and h = 6.626 × 1 0 - 34 J s is the Planck’s constant. The mass of the electron is, m = 9.1 × 1 0 - 31 kg From equation 1 ν ∘ = ν − m v e 2 2 h ........................... 2 By substituting value in this ν ∘ = 7 .21 × 10 14 Hz − 9 .1 × 10 − 31 kg 6 .0 × 10 5 m s - 1 2 2 6 .626 × 10 − 34 J s = 4 . 57 × 10 14 Hz Hence, the threshold frequency for the photoemission of electrons is 4 . 57 × 10 14 Hz .