Dual Nature of Radiation and Matter — Practice

Question 1

The threshold frequency of a metal is 5e14 Hz. Find the work function in eV (h = 4.14e-15 eV s).

Accepted Answer

phi = h nu0 = 4.14e-15 x 5e14 = 2.07 eV.

Question 2

Photoelectrons of max KE 1.5 eV are emitted by 300 nm light. Find the work function (hc = 1240 eV nm).

Accepted Answer

Photon energy = 1240/300 = 4.13 eV. phi = 4.13 - 1.5 = 2.63 eV.

Question 3

Find the de Broglie wavelength of a proton (m = 1.67e-27 kg) at 2e6 m/s.

Accepted Answer

lambda = h/(mv) = 6.63e-34/(1.67e-27 x 2e6) = 1.98e-13 m.

Question 4

Stopping potential is 1.2 V for 400 nm light. Find the work function.

Accepted Answer

Photon energy = 1240/400 = 3.1 eV. K_max = 1.2 eV. phi = 3.1 - 1.2 = 1.9 eV.

Question 5

Find the de Broglie wavelength of an electron accelerated through 100 V.

Accepted Answer

lambda = 12.27/sqrt(100) = 1.227 Angstrom = 1.227e-10 m.

Practice — Dual Nature of Radiation and Matter