A retarding potential of 0 . 5 V is required to block the movement of electrons from the cathode of a photoelectric cell when violet light of wavelength 4000 A o strikes its surface. Find the maximum energy of the electron emitted from the cathode surface when 3000 A o light strikes it.

According to the equation of the photoelectric emission K max = hc λ - ϕ where c , ν 0 are the velocity and wavelength of the radiation and ϕ = work function We have given, λ = 400 × 10 - 9 m , c = 3 × 10 8 m / s and h = 6 . 62 × 10 - 34 Js , Maximum KE= 0 . 5 V Substituting the values, we have, 0 . 5 = 6 . 6 × 10 - 34 × 3 × 10 8 400 × 10 - 9 × 1 . 6 × 10 - 19 - ϕ or ϕ = 3 . 09 - 0 . 5 = 2 . 59 eV When a light of wave length 3000 × 10 - 10 m is falling over the metal, then the equation becomes, K max = hc λ - ϕ = 6 . 62 × 10 - 34 × 3 × 10 8 3000 × 10 - 10 × 1 . 6 × 10 - 19 - 2 . 59 = 4 . 13 - 2 . 59 = 1 . 54 ev or 1 . 54 × 1 . 6 × 10 - 19 J = 2 . 45 × 10 - 19 J Hence, maximum energy is 2 . 45 eV .

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When ultraviolet light of wavelength $300 nm$ is incident on a metal plate, a negative potential of $0.54 V$ is required to stop the emission of photoelectrons. Calculate the energy of the incident photon and the work function for the metal in $e V$ .

Important Questions on Photoelectric Effect

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IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 38

How much retarding potential is required to stop the emission of photoelectrons, if the work function of the target material is

1.25 e V

and the wavelength of the incident light is

4400 \overset{o}{A}

(h = 6.62 \times 10^{- 34} Js)

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IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 39

A regarding potential of

0.5 V

is required to block the movement of electrons from the cathode of a photoelectric cell when violet light of wavelength

4000 \overset{o}{A}

strikes its surface. Find the work function of this surface.

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 39

A retarding potential of

0.5 V

is required to block the movement of electrons from the cathode of a photoelectric cell when violet light of wavelength

4000 \overset{o}{A}

strikes its surface. Find the threshold frequency.

EASY

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 39

A retarding potential of

0.5 V

is required to block the movement of electrons from the cathode of a photoelectric cell when violet light of wavelength

4000 \overset{o}{A}

strikes its surface. Find the energy light of wavelength

3000 \overset{o}{A}

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 39

A retarding potential of

0.5 V

is required to block the movement of electrons from the cathode of a photoelectric cell when violet light of wavelength

4000 \overset{o}{A}

strikes its surface. Find the maximum energy of the electron emitted from the cathode surface when

3000 \overset{o}{A}

light strikes it.

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 40

Find the frequency of light which ejects from a metal surface electrons which are fully stopped by a retarding potential of

3 V

. The photoelectric effect starts in this metal at a frequency of

6 \times 10^{14} s^{- 1} (h = 6.63 \times 10^{- 34} Js, e = 1.6 \times 10^{- 19} C)

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ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 41

Ultraviolet light of wavelength

800 \overset{o}{A}

and

700 \overset{o}{A}

, when allowed to fall on hydrogen atoms in their ground state, is found to liberate electrons with kinetic energies

1.8 e V

and

4.0 e V

respectively. Find the value of Planck's cosntant.

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ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 42

In an experiment of photoelectric effect, the graph of maximum kinetic energy $E_{k}$ of the emitted photoelectrons versus the frequency $v$ of the incident light is a straight line shown in the figure. Calculate threshold frequency.

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When ultraviolet light of wavelength 300 nm is incident on a metal plate, a negative potential of 0.54 V is required to stop the emission of photoelectrons. Calculate the energy of the incident photon and the work function for the metal in eV.

Important Questions on Photoelectric Effect

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When ultraviolet light of wavelength $300 nm$ is incident on a metal plate, a negative potential of $0.54 V$ is required to stop the emission of photoelectrons. Calculate the energy of the incident photon and the work function for the metal in $e V$ .