Answer:
c. 1.2×10¹⁵ Hz
Explanation:
Work Function: This is the minimum amount of energy a photon requires to liberate an electron from the surface of a metal.
Mathematically, it can be represented as
E' = hf' ................................... Equation 1
Where E' = work function of gold, f' = minimum frequency ( threshold frequency), h = Planck's constant
Making f' the subject of the equation,
f' = E'/h................................. Equation 2
Given: E' = 4.8 ev = 4.8×1.6×10⁻¹⁹ J = 7.68×1.6×10⁻¹⁹ J, h = 6.626×10⁻³⁴Js.
Substituting into equation 2
f' = 7.68×10⁻¹⁹/ 6.626×10⁻³⁴
f' = 1.16×10¹⁵ Hz.
f' ≈ 1.2×10¹⁵ Hz
Thus the minimum frequency = 1.2×10¹⁵ Hz
The right option is c. 1.2×10¹⁵ Hz
