When light of wavelength 378 nm falls on a potassium surface, electrons are emitted that have a maximum kinetic energy of 1.9 eV. What is the work function of potassium? The speed of light is 3 × 10^8 m/s and Planck's constant is 6.63 × 10^?34 J · s . Answer in units of eV
What is the cutoff wavelength
What is the threshold frequency?