# Physics Class 12 NCERT Solutions: Chapter 11 Dual Nature of Radiation and Matter Part 1

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Q: 1. Find the

(A) Maximum frequency, and

(B) Minimum wavelength of produced by 30 kV electrons.

Answer:

Potential of the electrons,

Hence, energy of the electrons,

Where,

Hence, the maximum frequency of produced is

(B) The minimum wavelength produced by theis given as:

Hence, the minimum wavelength of produced is.

Q: 2. The work function of caesium metal is. When light of frequency is incident on the metal surface, photoemission of electrons occurs. What is the

(A) Maximum kinetic energy of the emitted electrons,

(B) Stopping potential, and

(C) Maximum speed of the emitted photoelectrons?

Answer:

Work function of caesium metal,

Frequency of light,

(A)The maximum kinetic energy is given by the photoelectric effect as:

Where,

Hence, the maximum kinetic energy of the emitted electrons is .

(B)For stopping potential, we can write the equation for kinetic energy as:

Hence, the stopping potential of the material is.

(C)Maximum speed of the emitted photoelectrons

Hence, the relation for kinetic energy can be written as:

Where,

Hence, the maximum speed of the emitted photoelectrons is.

Q: 3. The photoelectric cut-off voltage in a certain experiment is. What is the maximum kinetic energy of photoelectrons emitted?

Answer:

Photoelectric cut-off voltage,

The maximum kinetic energy of the emitted photoelectrons is given as:

Where,

Charge on an electron

Therefore, the maximum kinetic energy of the photoelectrons emitted in the given experiment is.