Calculate the difference in energy (in joules) between a photon with λ = 680 nm (red) and a photon with λ = 442 nm (blue).

Light of wavelength 340 nm, 600 nm and 680 nm is incident on a metal. Electrons are not emitted from the metal, which of the following is the most likely scenario.     The energy of the photon for 600 nm light corresponds to the work function of the material.     The energy of the photon for 680 nm light corresponds to the work function of the material.     The work function is less than any of these photon energies.     The work function is more than any of these photon energies.     The energy of the photon for 340 nm light corresponds to the work function of the material.

Ultraviolet light with a single wavelength and with an intensity of 550 W/m² is incident normally on the surface of a metal that has a work function of 3.44 eV. Photoelectrons are emitted with a maximum speed of 420 km/s. Find the maximum possible rate of photoelectron emission from 1 cm² of the surface by imagining that every photon produces one photoelectron.

A typical red laser pointer has a power output of 1.50 mW and a wavelength of 680 nm. Find how many photons per second the laser emits in units of 10¹5 photons/sec. (A) 2.31 (B) 5.13 (C) 4.97 (D) 7.49 (E) 3.78