# Balbharati solutions for Physics 12th Standard HSC Maharashtra State Board chapter 14 - Dual Nature of Radiation and Matter [Latest edition]

## Chapter 14: Dual Nature of Radiation and Matter

Exercises
Exercises [Pages 322 - 323]

### Balbharati solutions for Physics 12th Standard HSC Maharashtra State Board Chapter 14 Dual Nature of Radiation and Matter Exercises [Pages 322 - 323]

Exercises | Q 1.1 | Page 322

Choose the correct option.

A photocell is used to automatically switch on the street lights in the evening when the sunlight is low in intensity. Thus it has to work with visible light. The material of the cathode of the photocell is ______.

• Zinc

• Aluminum

• Nickel

• Potassium

Exercises | Q 1.2 | Page 322

Choose the correct option.

Polychromatic (containing many different frequencies) radiation is used in an experiment on the photoelectric effect. The stopping potential ______.

• Will depend on the average wavelength

• Will depend on the longest wavelength

• Will depend on the shortest wavelength

• Does not depend on the wavelength

Exercises | Q 1.3 | Page 322

Choose the correct option.

An electron, a proton, an α-particle, and a hydrogen atom are moving with the same kinetic energy. The associated de Broglie wavelength will be longest for ______.

• Electron

• Proton

• α-particle

• Hydrogen atom

Exercises | Q 1.4 | Page 322

Choose the correct option.

If NRed and NBlue are the numbers of photons emitted by the respective sources of equal power and equal dimensions in unit time, then ______.

• NRed < NBlue

• NRed = NBlue

• NRed > NBlue

• NRed ≈ NBlue

Exercises | Q 1.5 | Page 322

Choose the correct option.

The equation E = pc is valid ______.

• For all sub-atomic particles

• is valid for an electron but not for a photon

• is valid for a photon but not for an electron

• is valid for both an electron and a photon

Exercises | Q 2.1 | Page 322

What is the photoelectric effect?

Exercises | Q 2.2 | Page 322

Can microwaves be used in the experiment on photoelectric effect?

Exercises | Q 2.3 | Page 322

Is it always possible to see the photoelectric effect with a red light?

Exercises | Q 2.4 | Page 322

Using the values of work function given in the following table, tell which metal will require the highest frequency of incident radiation to generate photocurrent.

Typical values of work function for some common metals

 Metal Work function (in eV) Potassium 2.3 Sodium 2.4 Calcium 2.9 Zinc 3.6 Silver 4.3 Aluminium 4.3 Tungsten 4.5 Copper 4.7 Nickel 5.0 Gold 5.1
Exercises | Q 2.5 | Page 322

What do you understand by the term wave-particle duality? Where does it apply?

Exercises | Q 3 | Page 322

Explain the inverse linear dependence of stopping potential on the incident wavelength in a photoelectric effect experiment.

Exercises | Q 4 | Page 322

It is observed in an experiment on the photoelectric effect that an increase in the intensity of the incident radiation does not change the maximum kinetic energy of the electrons. Where does the extra energy of the incident radiation go? Is it lost? State your answer with explanatory reasoning.

Exercises | Q 5 | Page 322

Explain what you understand by the de Broglie wavelength of an electron. Will an electron at rest have an associated de Broglie wavelength? Justify your answer.

Exercises | Q 6 | Page 322

State the importance of Davisson and Germer experiment.

Exercises | Q 7 | Page 322

What will be the energy of each photon in monochromatic light of frequency 5 ×1014Hz?

Exercises | Q 8 | Page 323
Observations from an experiment on the photoelectric effect for the stopping potential by varying the incident frequency were plotted. The slope of the linear curve was found to be approximately 4.1 × 10−15 V s. Given that Exercises the charge of an electron is 1.6 × 10−19 C, find the value of the Planck’s constant h.
Exercises | Q 9 | Page 323

The threshold wavelength of tungsten is 2.76 x 10-5 cm.
(a) Explain why no photoelectrons are emitted when the wavelength is more than 2.76 x 10-5 cm.
(b) What will be the maximum kinetic energy of electrons ejected in each of the following cases

(i) if ultraviolet radiation of wavelength λ = 1.80 × 10-5 cm and
(ii) radiation of frequency 4 x 1015 Hz is made incident on the tungsten surface?

Exercises | Q 10 | Page 323

Photocurrent recorded in the microammeter in an experimental setup of the photoelectric effect vanishes when the retarding potential is more than 0.8 V if the wavelength of incident radiation is 4950 Å. If the source of incident radiation is changed, the stopping potential turns out to be 1.2 V. Find the work function of the cathode material and the wavelength of the second source.

Exercises | Q 11 | Page 323

Radiation of wavelength 4500 Å is incident on a metal having work function 2.0 eV. Due to the presence of a magnetic field B, the most energetic photoelectrons emitted in a direction perpendicular to the field move along a circular path of radius 20 cm. What is the value of the magnetic field B?

Exercises | Q 12 | Page 323

Given the following data for incident wavelength and the stopping potential obtained from an experiment on the photoelectric effect, estimate the value of Planck's constant and the work function of the cathode material. What is the threshold frequency and corresponding wavelength? What is the most likely metal used for emitter?

 Incident wavelength (in Å) 2536 3650 Stopping potential (in V) 1.95 0.5
Exercises | Q 13.1 | Page 323

Calculate the wavelength associated with an electron, its momentum and speed when it is accelerated through a potential of 54 V.

Exercises | Q 13.2 | Page 323

Calculate the wavelength associated with an electron, its momentum and speed when it is moving with the kinetic energy of 150 eV.

Exercises | Q 14 | Page 323

The de Broglie wavelengths associated with an electron and a proton are the same. What will be the ratio of (i) their momenta (ii) their kinetic energies?

Exercises | Q 15 | Page 323

Two particles have the same de Broglie wavelength and one is moving four times as fast as the other. If the slower particle is an α-particle, what are the possibilities for the other particle?

Exercises | Q 16 | Page 323

What is the speed of a proton having de Broglie wavelength of 0.08 Å?

Exercises | Q 17 | Page 323

In nuclear reactors, neutrons travel with energies of 5 × 10-21J. Find their speed and wavelength.

Exercises | Q 18 | Page 323

Find the ratio of the de Broglie wavelengths of an electron and a proton when both are moving with the (a) same speed, (b) the same kinetic energy, and (c) the same momentum. State which of the two will have a longer wavelength in each case.

Exercises

## Balbharati solutions for Physics 12th Standard HSC Maharashtra State Board chapter 14 - Dual Nature of Radiation and Matter

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Concepts covered in Physics 12th Standard HSC Maharashtra State Board chapter 14 Dual Nature of Radiation and Matter are Dual Nature of Radiation and Matter, The Photoelectric Effect, Wave-particle Duality of Electromagnetic Radiation, Photo Cell, De Broglie Hypothesis, Davisson and Germer Experiment, Wave-particle Duality of Matter.

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