Final answer:
The difference in work function between two surfaces is determined by the difference in maximum kinetic energy of photo-electrons ejected when irradiated with light of the same frequency, which is given as 1.20 x 10^-19 J.
Step-by-step explanation:
The difference in the work function for the two surfaces can be calculated by using the principle of the photoelectric effect. According to the effect, the maximum kinetic energy (KE) of photo-electrons ejected from a surface when irradiated by light of a particular frequency (f) is given by the equation KE = hf - Φ, where 'h' is Planck's constant, 'f' is the frequency of the incident light, and Φ is the work function of the surface.
Since the frequency is the same for both surfaces, we have:
KE_A = hf - Φ_A
KE_B = hf - Φ_B
The difference in kinetic energy between the two surfaces is given by:
ΔKE = KE_A - KE_B
ΔKE = (hf - Φ_A) - (hf - Φ_B)
ΔKE = Φ_B - Φ_A
Given that ΔKE = 1.20 x 10-19 J, the difference in work function is:
Φ_B - Φ_A = 1.20 x 10-19 J
The energy of a photon can be calculated using the equation E = hf, where E is the energy, h is Planck's constant (approximately 6.626 x 10^-34 J*s), and f is the frequency of the light. The work function, represented by the symbol φ, is the minimum energy required to remove an electron from the surface of a material.
The maximum kinetic energy of the ejected electrons can be determined using the equation KE = hf - φ. From the question, we know that the frequency of light for surface A is 7.20 Hz and the difference in maximum kinetic energy between surface A and surface B is 1.20 x 10^-19 J.
Therefore, the difference in work function is equal to the difference in maximum kinetic energy, which is 1.20 x 10^-19 J.