chemistry...?

Question

It requires a photon with a minimum energy of 4.41 x 10-19 J to emit electrons from sodium metal. (a) What is the minimum frequency of light necessary to emit electrons from sodium via the photoelectric effect? (b)What is the wavelength of this light? (c) If sodium is irradiated with light of 439 nm, what is the maximum possible kinetic energy of the emitted electrons?
(d) What is the maximum number of electrons that can be freed by a burst of light whose total energy is 1.00 μJ?

Answer 1

(a) E = h *nu (E = energy, h = Planck's constant, nu = frequency). You are given E (4.41 x 10^-19 J), and h should be in your chemistry textbook. Solve for nu.

(b) nu*lambda = c (nu = frequency, lambda = wavelength, c = speed of light).

Assuming you solved (a) correctly, you should use the value of nu obtained in (a), and the speed of light as in your textbook, solving for the wavelength lambda.

(c) E = h*nu again, only this time, you need to use that equation from b:
nu * lambda = c.
nu = c / lambda
Thus, E = h * nu
E = h * c / lambda
***NOTE*** you have to be wary of the units of Joules. Remember, one J = 1 (kg * m*m) / (s*s). Since your wavelength, nu, is in nm, and your speed of light, c, is in m / s, you will need to convert nu into meters to be consistent.

(d) This is a simple division problem. Convert microjoules to joules, then divide that number by the energy of release of a single electron (4.41 x 10^-19 J).