Tamil Nadu Board of Secondary EducationHSC Science Class 12th

# Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Physics Volume 1 and 2 Answers Guide chapter 9 - Atomic and Nuclear physics [Latest edition]

#### Chapters ## Chapter 9: Atomic and Nuclear physics

Evaluation
Evaluation [Pages 189 - 190]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Physics Volume 1 and 2 Answers Guide Chapter 9 Atomic and Nuclear physicsEvaluation [Pages 189 - 190]

#### Multiple Choice Questions

Evaluation | Q 1. | Page 189

Suppose an alpha particle accelerated by a potential of V volt is allowed to collide with a nucleus whose atomic number is Z, then the distance of closest approach of alpha particle to the nucleus is ______.

• 14.4 $\frac{\text{Z}}{\text{V}}$Å

• 14.4 $\frac{\text{V}}{\text{Z}}$Å

• 1.44 $\frac{\text{Z}}{\text{V}}$Å

• 1.44 $\frac{\text{V}}{\text{Z}}$Å

Evaluation | Q 2. | Page 189

In a hydrogen atom, the electron revolving in the fourth orbit, has angular momentum equal to ______.

• h

• "h"/pi

• (4"h")/pi

• (2"h")/pi

Evaluation | Q 3. | Page 189

Atomic number of H-like atom with ionization potential 122.4 V for n = 1 is ______.

• 1

• 2

• 3

• 4

Evaluation | Q 4. | Page 189

The ratio between the first three orbits of a hydrogen atom is ______.

• 1 : 2 : 3

• 2 : 4 : 6

• 1 : 4 : 9

• 1 : 3 : 5

Evaluation | Q 5. | Page 189

The charge of cathode rays is ______.

• positive

• negative

• neutral

• not defined

Evaluation | Q 6. | Page 189

In J.J. Thomson e/m experiment, a beam of electron is replaced by that of muons (particle with same charge as that of electrons but mass 208 times that of electrons). No deflection condition is achieved only if

• B is increased by 208 times

• B is decreased by 208 times

• B is increased by 14.4 times

• B is decreased by 14.4 times

Evaluation | Q 7. | Page 189

The ratio of the wavelengths for the transition from n =2 to n = 1 in Li++, He+ and H is ______.

• 1 : 2 : 3

• 1 : 4 : 9

• 3 : 2 : 1

• 4 : 9 : 36

Evaluation | Q 8. | Page 189

The electric potential between a proton and an electron is given by V = V0 In ("r"/"r"_0), where ris a constant. Assume that Bohr atom model is applicable to potential, then a variation of radius of nth orbit rn with the principal quantum number n is

• "r"_"n" prop 1/"n"

• rn ∝ n

• "r"_"n" prop 1/"n"^2

• rn ∝ n2

Evaluation | Q 9. | Page 189

If the nuclear radius of 27Al is 3.6 fermi, the approximate unclear radius of 64 Cu is ______.

• 2.4

• 1.2

• 4.8

• 3.6

Evaluation | Q 10. | Page 189

The nucleus is approximately spherical in shape. Then the surface area of nucleus having mass number A varies as ______.

• A2/3

• A4/3

• A1/3

• A5/3

Evaluation | Q 11. | Page 189

The mass of a $\ce{^7_3Li}$ nucleus is 0.042 u less than the sum of the masses of all its nucleons. The binding energy per nucleon of $\ce{^7_3Li}$ nucleus is nearly ______.

• 46 MeV

• 5.6 MeV

• 3.9 MeV

• 23 MeV

Evaluation | Q 12. | Page 190

Mp denotes the mass of the proton and Mn denotes mass of a neutron. A given nucleus of binding energy B, contains Z protons and N neutrons. The mass M (N, Z) of the nucleus is given by(where c is the speed of light)

• M (N, Z) = NMn + ZMp – Bc2

• M (N, Z) = NMn + ZMp + Bc2

• M (N, Z) = NMn + ZMp – B / c2

• M (N, Z) = NMn + ZMp + B / c2

Evaluation | Q 13. | Page 190

A radioactive nucleus (initial mass number A and atomic number Z) emits 2α and 2 positrons. The ratio of a number of neutrons to that of protons in the final nucleus will be ______.

• ("A" - "Z" - 4)/("Z" - 2)

• ("A" - "Z" - 2)/("Z" - 6)

• ("A" - "Z" - 4)/("Z" - 6)

• ("A" - "Z" - 12)/("Z" - 4)

Evaluation | Q 14. | Page 190

The half-life period of radioactive element A is the same as the mean life time of another radioactive element B. Initially both have the same number of atoms. Then

• A and B have the same decay rate initially

• A and B decay at the same rate always

• B will decay at faster rate than A

• A will decay at faster rate than B.

Evaluation | Q 15. | Page 190

A radiative element has N0 number of nuclei at t = 0. The number of nuclei remaining after half of a half-life (that is, at time t = 1/2 "T" _(1/2)).

• "N"_0/2

• "N"_0/sqrt2

• "N"_0/4

• "N"_0/8

Evaluation [Pages 190 - 191]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Physics Volume 1 and 2 Answers Guide Chapter 9 Atomic and Nuclear physicsEvaluation [Pages 190 - 191]

Evaluation | Q II. 1. | Page 190

What are cathode rays?

Evaluation | Q II. 2. | Page 190

Write the properties of cathode rays.

Evaluation | Q II. 3. | Page 190

Give the results of Rutherford alpha scattering experiment.

Evaluation | Q II. 4. | Page 190

Write down the postulates of Bohr atom model.

Evaluation | Q II. 5. | Page 190

What is meant by excitation energy?

Evaluation | Q II. 6. | Page 190

Define the ionization energy.

Evaluation | Q II. 6. | Page 190

Define the ionization potential.

Evaluation | Q II. 7. | Page 190

Write down the draw backs of the Bohr atom model.

Evaluation | Q II. 8. | Page 190

What is distance of closest approach?

Evaluation | Q II. 9. | Page 190

Define impact parameter.

Evaluation | Q II. 10. | Page 190

Write a general notation of the nucleus of element X. What each term denotes?

Evaluation | Q II. 11. | Page 190

What is isotope? Give an example.

Evaluation | Q II. 12. | Page 190

What is isotone? Give an example.

Evaluation | Q II. 13. | Page 190

What is isobar? Give an example.

Evaluation | Q II. 14. | Page 190

Define atomic mass unit u.

Evaluation | Q II. 15. | Page 190

Show that nuclear density is almost constant for nuclei with Z > 10.

Evaluation | Q II. 16. | Page 190

What is mass defect?

Evaluation | Q II. 17. | Page 190

What is binding energy of a nucleus? Give its expression.

Evaluation | Q II. 18. | Page 190

Calculate the energy equivalent of 1 atomic mass unit.

Evaluation | Q II. 19. | Page 190

Give the physical meaning of binding energy per nucleon.

Evaluation | Q II. 20. | Page 190

Evaluation | Q II. 21. | Page 191

Give the symbolic representation of alpha decay, beta decay and gamma emission.

Evaluation | Q II. 22. | Page 191

In alpha decay, why the unstable nucleus emits $\ce{^4_2He}$ nucleus? Why it does not emit four separate nucleons?

Evaluation | Q II. 23. | Page 191

What is mean life of nucleus? Give the expression.

Evaluation | Q II. 24. | Page 191

What is half-life of nucleus? Give the expression.

Evaluation | Q II. 25. | Page 191

What is meant by activity or decay rate? Give its unit.

Evaluation | Q II. 26. | Page 191

Define curie.

Evaluation | Q II. 27. | Page 191

What are the constituent particles of neutron and proton?

Evaluation [Page 191]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Physics Volume 1 and 2 Answers Guide Chapter 9 Atomic and Nuclear physicsEvaluation [Page 191]

Evaluation | Q III. 1. | Page 191

Explain the J. J. Thomson experiment to determine the specific charge of an electron.

Evaluation | Q III. 2. | Page 191

Discuss the Millikan’s oil drop experiment to determine the charge of an electron.

Evaluation | Q III. 3. | Page 191

Derive the energy expression for an eletron is the hydrogen atom using Bohr atom model.

Evaluation | Q III. 4. | Page 191

Discuss the spectral series of hydrogen atom.

Evaluation | Q III. 5. | Page 191

Explain the variation of average binding energy with the mass number using a graph and discuss about its features.

Evaluation | Q III. 6. | Page 191

Explain in detail the nuclear force.

Evaluation | Q III. 7. | Page 191

Discuss the alpha decay process with example.

Evaluation | Q III. 8. | Page 191

Discuss the beta decay process with examples.

Evaluation | Q III. 9. | Page 191

Discuss the gamma decay process with an example.

Evaluation | Q III. 10. | Page 191

Evaluation | Q III. 11. | Page 191

Discuss the properties of neutrino and its role in beta decay.

Evaluation | Q III. 12. | Page 191

Explain the idea of carbon dating.

Evaluation | Q III. 13. | Page 191

Discuss the process of nuclear fission and its properties.

Evaluation | Q III. 14. | Page 191

Discuss the process of nuclear fusion and how energy is generated in stars?

Evaluation | Q III. 15. | Page 191

Describe the working of nuclear reactor with a block diagram.

Evaluation | Q III. 16. | Page 191

Explain in detail the four fundamental forces in nature.

Evaluation | Q III. 17. | Page 191

Briefly explain the elementary particles present in nature.

Evaluation [Pages 191 - 192]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Physics Volume 1 and 2 Answers Guide Chapter 9 Atomic and Nuclear physicsEvaluation [Pages 191 - 192]

#### Exercises

Evaluation | Q 1. | Page 191

Consider two hydrogen atoms HA and HB in ground state. Assume that hydrogen atom HA is at rest and hydrogen atom HB is moving with a speed and make head-on collide on the stationary hydrogen atom HA. After the strike, both of them move together. What is the minimum value of the kinetic energy of the moving hydrogen atom HB, such that any one of the hydrogen atoms reaches one of the excitation state?

Evaluation | Q 2. | Page 192

In the Bohr atom model, the frequency of transitions is given by the following expression

v = "Rc" (1/"n"^2 - 1/"m"^2), where n < m

Consider the following transitions:

 Transitions m → n 1 3 → 2 2 2 → 1 3 3 → 1

Show that the frequency of these transitions obey sum rule (which is known as Ritz combination principle).

Evaluation | Q 3. | Page 192
1. A hydrogen atom is excited by radiation of wavelength 97.5 nm. Find the principal quantum number of the excited state.
2. Show that the total number of lines in emission spectrum is ("n"("n - 1"))/2.
Compute the total number of possible lines in emission spectrum as given in(a).
Evaluation | Q 4. | Page 192

Calculate the radius of the earth if the density of the earth is equal to the density of the nucleus. [mass of earth 5.97 x 1024 kg].

Evaluation | Q 5. | Page 192

Calculate the mass defect and the binding energy per nucleon of the $\ce{^108_47Ag}$ nucleus. [atomic mass of Ag = 107.905949].

Evaluation | Q 6. | Page 192

Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes respectively. Initially, the samples have equal number of nuclei. Calculate the ratio of decayed numbers of A and B nuclei after 80 minutes.

Evaluation | Q 7. | Page 192

On your birthday, you measure the activity of the sample 210Bi which has a half-life of 5.01 days. The initial activity that you measure is 1µCi.

1. What is the approximate activity of the sample on your next birthday? Calculate
2. the decay constant
3. the mean life
4. initial number of atoms.
Evaluation | Q 8. | Page 192

Calculate the time required for 60% of a sample of radon to undergo decay. Given T1/2 of radon = 3.8 days.

Evaluation | Q 9. | Page 192

Assuming that energy released by the fission of a single $\ce{^235_92U}$ nucleus is 200MeV, calculate the number of fissions per second required to produce 1-watt power.

Evaluation | Q 10. | Page 192

Show that the mass of radium $\ce{^226_88Ra}$ with an activity of 1 curie is almost a gram. Given T1/2 = 1600 years.

Evaluation | Q 11. | Page 192

Characol pieces of tree is found from an archeological site. The carbon-14 content of this characol is only 17.5% that of equivalent sample of carbon from a living tree. What is the age of tree?

## Chapter 9: Atomic and Nuclear physics

Evaluation ## Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Physics Volume 1 and 2 Answers Guide chapter 9 - Atomic and Nuclear physics

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Concepts covered in Class 12th Physics Volume 1 and 2 Answers Guide chapter 9 Atomic and Nuclear physics are Nuclei, Nuclear Force, Radioactivity, Nuclear Fission, Nuclear Fusion – Energy Generation in Stars, Introduction to Atomic and Nuclear Physics, Electric Discharge Through Gases, Introduction to Atom Models.

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