Question

Electromagnetic radiation whose electric component varies with time as E(t)=E0​cos(ωt+ϕ), where E0​ and ϕ are constants, is incident on lithium and liberates photoelectrons. If the kinetic energy of the most energetic electrons be K, given that ℏ and ν (frequency) are constants, the work function of lithium is (take Planck's constant h).

Options:
a. hν−K
b. hν+K
c. hνsinϕ−K
d. hνcosϕ−K

Answer 1

The work function of lithium is determined using Einstein's photoelectric equation KE = hf - BE, and since the only value that affects the work function in this context is the photon energy hf and the kinetic energy K, the work function is BE = hf - K. Therefore, option (a) hν - K is correct.

Step-by-step explanation:

The work function of lithium in the context of the photoelectric effect can be determined using Einstein's equation for the maximum kinetic energy of photoelectrons, which is given by KE = hf - BE, where KE is the maximum kinetic energy of the ejected electron, hf is the energy of the incident photon, and BE is the binding energy or work function of the material. Here, hf represents the energy of photons corresponding to the electromagnetic radiation with frequency 'ν'. Since the kinetic energy of the most energetic electrons is given as K, and the equation does not depend upon the phase (φ) or electric field amplitude (E0), the work function of lithium is given by BE = hf - K. Therefore, the correct answer is hν - K, which means option (a) is the correct choice.