Question

Please show steps and show equations used

5. The cut-off (threshold) wavelength for the photoelectric effect for silver is 325 nm. (a) (4 pts) Find the maximum speed of electrons ejected from a silver surface by ultraviolet light of wavelength 250 nm. (b) (2 pts) What would happen if the intensity of light at wavelength 250 nm were increased? (o) 2 pts) If the silver surface were illuminated by a light of wavelength 500 nm, what would happen? Explain (d) (2 pts) On the grid below, graph the maximum kinetic energy of photoelectrons (in eV) as function of frequency of light. Put appropriate numerical values on the axes. 바야八 GOR en (M. 사

Answer 1

Light is made of photos, when photos hit the silver surface, they are absorbed by silver atoms. If photons carry sufficient energy they might knock electron out of the silver atom. Lets consider a single photoelectric process. A photon of energy E, is absorbed by a silver atom. Let the energy required to free an electron from the atom is phi (also known as work function). If E > phi, the amount of energy remaining after free the electron is manifested as the kinetic energy of the electron. Mathematically, K = E - phi The light of wavelength lambda contains photons, each of energy E = hC/lambda At threshold, the energy is equal to phi, that electron is only set free, and it has zero kinetic energy 0 = hC/lambda_- phi Rightarrow phi = hC/lambda_0 Therefore K = hC/lambda - hC/lambda_0 \r\n we know that K = 1/2mv^2 m is the mass of an electron 1/2 mv^2 = hC(1/lambda - 1/lambda_0) Rightarrow v = squareroot 2hC/m(1/lambda - 1/lambda_0)