What is the longest wavelength of radiation in the following metals?

Question

In his explanation of the threshold frequency in the photoelectric effect, Einstein reasoned that the absorbed photon must have the minimum energy required to dislodge an electron from the metal surface. This energy is called the work function () of that metal. What is the longest wavelength of radiation (in nm) that could cause the photoelectric effect in each of the following metals?
(a) Barium, = 4.3 10-19 J
nm
(b) Tantalum, = 6.41 10-19 J
nm
(c) Tungsten, = 7.16 10-19 J
nm

Answer 1

It seems to me that you have trouble in electro-photon reaction. Please memorize the formula between the energy and frequency or wavelength.
To convert energy to frequency or wavelength, we have to use the following formula:
E = h•f = h•c/L
where h the Plank constant 6.626x10^-34 J•s, f the frequency in 1/s, c the speed of light 2.998x10^8m/s, and L the wavelength in m (1nm = 10^-9m). Now please do the math.