For a photoelectric material with a work function of 4.0 eV , calculate the wavelength of incident light that results in a stopping potential of 2.5 V .

Correct answer: B. 191 nm According to Einstein's photoelectric equation: E = + K_ Given work function = 4.0 eV and stopping potential V_0 = 2.5 V . The maximum kinetic energy of the photoelectrons is K_ = eV_0 = 2.5 eV . The energy of the incident photon is: E = 4.0 eV + 2.5 eV = 6.5 eV The wavelength of the incident light is given by λ = (hc)/(E) . Using hc 1240 eV : λ = (1240)/(6.5) 191 nm

Concepts Of Physics MCQ Edition [Volume 2]

Exam: Concepts Of Physics MCQ Edition [Volume 2]
Subject: Physics
Chapter: Photoelectric Effect and Wave–Particle Duality

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Photoelectric Effect and Wave–Particle Duality

For a photoelectric material with a work function of 4.0 eV ,...

For a photoelectric material with a work function of

4.0 \text{ eV}

, calculate the wavelength of incident light that results in a stopping potential of

2.5 \text{ V}

Options

A $496 \text{ nm}$
B $191 \text{ nm}$
C $310 \text{ nm}$
D $827 \text{ nm}$

Correct answer

B. $191 \text{ nm}$

Step-by-step solution

According to Einstein's photoelectric equation:

E = \Phi + K_\max

Given work function

\Phi = 4.0 \text{ eV}

and stopping potential

V_0 = 2.5 \text{ V}

.

The maximum kinetic energy of the photoelectrons is

K_\max = eV_0 = 2.5 \text{ eV}

.

The energy of the incident photon is:

E = 4.0 \text{ eV} + 2.5 \text{ eV} = 6.5 \text{ eV}

The wavelength of the incident light is given by

\lambda = \dfrac{hc}{E}

.

Using

hc \approx 1240 \text{ eV}\cdot\text{nm}

\lambda = \dfrac{1240}{6.5} \approx 191 \text{ nm}

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