Find the energy of a photon of frequency 6.43 x 10^14 Hz. Let 1 eV = 1.60 × 10−19 J and Planck's constant h = 4.136 × 10−15 eV ∙ s. A. 3.27 eV
B. 1.62 eV
C. 1.94 eV
D. 2.66 eV

A photocathode has a work function is 2.5 eV. It is illuminated with white light that has a continuous wavelength band from 360 nm to 700 nm. What is the stopping potential for this white light illumination? Let 1 eV = 1.60 × 10^−19 J, the mass of an electron m = 9.11 × 10^−31 kg, the speed of light c = 3.00 × 108 m/s, and Planck's constant h = 4.136 × 10^−15 eV ∙ s.
A. 1.1 V
B. 0.85 V
C. 0.94 V
D. 1.2 V
E. 1.0 V