Correct Answer - Option 1 : 2.4 × 10
-19 J
Concept:
Photoelectric effect: When the light of a sufficiently small wavelength is incident on the metal surface, electrons are ejected from the metal instantly. This phenomenon is called the photoelectric effect.
Mathematically it is
\( h\nu = \phi + K.E \)
\(\nu = \frac{h}{\lambda }\)
Stopping potential: The photocurrent may be stopped by applying a negative potential to anode w.r.t. cathode. The minimum potential required to stop the electron emitted from metal so that its kinetic energy becomes zero.
Mathematically,
The stopping potential (eV) is:
\( K.{E_{\max }} = \frac{{hc}}{\lambda } - \phi = h\nu - \phi \)
Work function: It is the minimum amount of energy required so that metal emits an electron.
- It is represented with ϕ
- Its unit is eV or joules.
- It is having different values for different metals.
In photo electric effect
(ϕ) = (h c /λ ) - K.E. (electrons)
Where h = planks constant = 6.6 × 10-34 = 4.14 × 10-15 eV-s, ν = incident frequency, ϕ = work function, c = speed of light, λ = wavelength,
e = 1.6× 1019 coulomb.
Calculation:
Given that: ϕ = 2.4 eV, hν = 3.9 eV
We have,
\(K.{E_{\max }} = \frac{{hc}}{\lambda } - \phi = h\nu - \phi \)
But, E = hν - ϕ = 3.9 - 2.4 = 1.5 eV = 1.5 × 1.6 × 10-19 = 2.4 × 10-19
The maximum kinetic energy of the photoelectrons produced is 2.4 × 10-19
