Using E = hf and work function φ = 2.2 eV, with hf = 3.5 eV, calculate the kinetic energy of emitted electrons.

Using E = hf and work function φ = 2.2 eV, with hf = 3.5 eV, calculate the kinetic energy of emitted electrons.

• A. 0.9 eV
• B. 1.0 eV
• C. 1.3 eV
• D. 1.5 eV

Answer: (C)

In the photoelectric effect, the energy of each incoming photon goes first into overcoming the work function, and any leftover energy becomes the kinetic energy of the emitted electron. So the kinetic energy KE = hf − φ. Here hf = 3.5 eV and φ = 2.2 eV, so KE = 3.5 − 2.2 = 1.3 eV. Since hf exceeds φ, emission occurs with electrons carrying 1.3 eV of kinetic energy.

In the photoelectric effect, the energy of each incoming photon goes first into overcoming the work function, and any leftover energy becomes the kinetic energy of the emitted electron. So the kinetic energy KE = hf − φ.

Here hf = 3.5 eV and φ = 2.2 eV, so KE = 3.5 − 2.2 = 1.3 eV. Since hf exceeds φ, emission occurs with electrons carrying 1.3 eV of kinetic energy.