A stopping potential of 0.50 V is required when a phototube is illuminated with monochromatic light of wavelength 590 nm. Monochromatic light of a different wavelength is now shown on the tube, and the stopping potential is measured to be 2.30 V. What is the wavelength of this new light? (c = 3.00 × 10⁸ m/s, e = - 1.60 × 10^-19 C, h = 6.626 × 10^-34 J ∙ s, 1 eV = 1.60 × 10^-19 J) A) 320 nm B) 300 nm C) 340 nm D) 360 nm E) 410 nm

Question

Quizplus · Accepted Answer

The correct answer is A because the energy of the incident photon is equal to the work function of the metal plus the kinetic energy of the emitted electron. The work function is a constant for a given metal, so the kinetic energy of the emitted electron is proportional to the energy of the incident photon. The energy of a photon is inversely proportional to its wavelength, so the shorter the wavelength of the incident light, the greater the kinetic energy of the emitted electron. Therefore, the stopping potential, which is proportional to the kinetic energy of the emitted electron, will be greater for shorter wavelengths of incident light.

A Stopping Potential of 0