**NEET AIPMT Physics Chapter Wise Solutions – Atoms and Nuclei**

**1. nucleus of uranium decays at rest into nuclei of thorium and helium. Then (AIPMT 2015)**

(a) The helium nucleus has more momentum than the thorium nucleus.

(b) The helium nucleus has less kinetic energy than the thorium nucleus.

(c) The helium nucleus has more kinetic energy than the thorium nucleus.

(d) The helium nucleus has less momentum than the thorium nucleus.

**2. In the spectrum of hydrogen, the ratio of the I longest wavelength in the Lyman series to the i longest wavelength in the Balmer series is (AIPMT 2015)**

(a) 27/5

(b) 5/27

(c) 4/9

(d) 9/4

**3. If radius of the ^{27}_{13}Al**

**nucleus is taken to be R**

_{Al}, then the radius of^{125}_{53}Te nucleus is nearly (AIPMT 2015, Cancelled)**4. Consider 3 ^{rd} orbit of He^{+} (Helium), using non- relativistic approach, the speed of electron in this orbit will be [given K = 9 x 10^{9} constant, Z = 2 and h (Planck’s Constant) = 6.6 x 10 ^{-34} J s] (AIPMT 2015, Cancelled)**

(a) 0.73 x 10^{6 }m/s

(b) 3.0 x 10^{8 }m/s

(c) 2.92 x 10^{6} m/s

(d) 1.46 x 10^{8} m/s

**5. Hydrogen atom in ground state is excited by a monochromatic radiation of λ = 975 Å. Number of spectral lines in the resulting spectrum emitted will be (AIPMT 2014)**

(a) 3

(b) 2

(c) 6

(d) 10

**6. The binding energy per nucleon of and nuclei are 5.60 MeV and 7.06 MeV respectively. In the nuclear reaction**

** **

** the value of energy Q released is (AIPMT 2014)**

(a) 19.6 MeV

(b) -2.4 MeV

(c) 8.4 MeV

(d) 17.3 MeV

**7. A radioisotope X with a half life 1.4 x 10 ^{9} years decays to Y which is stable. A sample of the rock from a cave was found to contain X and Y in the ratio 1:7. The age of the rock is (AIPMT 2014)**

(a) 1.96 x 10^{9} years

(b) 3.92 x 10^{9} years

(c) 4.20 x 10^{9} years

(d) 8.40 x 10^{9} years

**8. Ratio of longest wave lengths corresponding to Lyman and Balmer series in hydrogen spectrum is (MEET 2013)**

(a) 7/29

(b) 9/31

(c) 5/27

(d) 3/23

**9. A certain mass of Hydrogen is changed to Helium by the process of fusion. The mass defect in fusion reaction is 0.02866 u. The energy liberated per u is (given 1 u = 931 MeV) (MEET 2013)**

(a) 6.675 MeV

(b) 13.35 MeV

(c) 2.67 MeV

(d) 26.7 MeV

**10. The half life ofa radioactive isotope ‘X’ is 20 years. It decays to another element ‘Y’ which is stable. The two elements ‘X’ and ‘ Y’ were found to be in the ratio 1 : 7 in a sample of a given rock. The age of the rock is estimated to be (NEET 2013)**

(a) 80 years

(b) 100 years

(c) 40 years

(d) 60 years

**11. How does the Binding Energy per nucleon vary with the increase in the number of nucleons? (Karnataka NEET 2013)**

(a) Decrease continuously with mass number.

(b) First decreases and then increases with increase in mass number.

(c) First increases and then decreases with increase in mass number.

(d) Increases continuously with mass number.

**12. An electron in hydrogen atom makes a transition n _{1} —> n_{2} where n_{1} and n_{2} are principal quantum numbers of the two states. Assuming Bohr’s model to be valid, the time period of the electron in the initial state is eight times that in the final state. The possible values of n_{1} and n_{2} are (Karnataka NEET 2013)**

(a) n_{1} = 6 and n_{2} = 2

(b) n_{1} = 8 and n_{2}=1

(c) n_{1} = 8 and n_{2} = 2

(d) n_{1} = 4 and n_{2} = 2

**13. α-particles, β-particles and γ-rays are all having same energy. Their penetrating power in a given medium in increasing order will be (Karnataka NEET 2013)**

(a) γ,α,β

(b) α, β,γ

(c) β, α,γ

(d) β,γ,α

**14. Electron in hydrogen atom first jumps from third excited state to second excited state and then from second excited to the first excited state. The ratio of the wavelengths λ _{1} : λ_{2} emitted in the two cases (Prelims 2012)**

(a) 7/5

(b) 27/20

(c) 27/5

(d) 20/7

**15. If the nuclear radius of ^{27}Al is 3.6 fermi, the approximate nuclear radius of ^{64}Cu in fermi is (Prelims 2012)**

(a)4

(b) 1.2

(c) 4.8

(d) 3.6

**16. A mixture consists of two radioactive materials A _{1} and A_{2} with half lives of 20 s and 10 s respectively. Initially the mixture has 40 g of 4, and 160 g of A_{r} The amount of the two in the mixture will become equal after (Prelims 2012)**

(a) 60s

(b) 80s

(c) 20 s

(d) 40 s

**17. An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be (m is the mass of the electron, R, Rydberg constant and h Planck’s constant)**

**18. The transition from the state n = 3 to n=1 in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from (Mains 2012 )**

(a) 2—>1

(b) 3 —>2

(c) 4 —>2

(d) 4—>3

**19. The half life of a radioactive nucleus is 50 days. The time interval (t _{2} – t_{1}) between the time t_{2 }when 2/3 of it has decayed and the time t_{1} when 1/3 of it had decayed is (Mains 2012 )**

(a) 30 days

(b) 50 days

(c) 60 days

(d) 15 days

**20. The wavelength of the first line of Lyman series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen like ion. The atomic number Z of hydrogen like ion is (Prelims 2011)**

(a) 3

(b) 4

(c) 1

(d) 2

**21. The half life of a radioactive isotope X is 50 years. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio of 1 : 15 in a sample of a given rock. The age of the rock was estimated to be (Prelims 2011 )**

(a) 150 years

(b) 200 years

(c) 250 years

(d) 100 years

**22. The power obtained in a reactor using U ^{235 }disintegration is 1000 kW. The mass decay of U^{235 }per hour is (Prelims 2011)**

(a) 10 microgram

(b) 20 microgram

(c) 40 microgram

(d) 1 microgram

**23. A radioactive nucleus of mass M emits a photon of frequency υ and the nucleus recoils. The recoil energy will be ( Prelims 2011)**

(a) Mc^{2} – hυ

(b) h^{2}υ^{2}/2Mc^{2
}(c) zero

(d) hυ

**24. A nucleus ^{m}_{n}X emits one a particle and two α-particles. The resulting nucleus is ( Prelims 2011)**

**25. Fusion reaction takes place at high temperature because ( Prelims 2011)**

(a) nuclei break up at high temperature

(b) atoms get ionised at high temperature

(c) kinetic energy is high enough to overcome the coulomb repulsion between nuclei

(d) molecules break up at high temperature

**26. An electron in the hydrogen atom jumps-Trom excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is 10 V, then the value of n is (Mains 2011)**

(a) 2

(b) 3

(c) 4

(d) 5

**27. Two radioactive nuclei P and Q, in a given sample decay into a stable nucleus At time t = 0, number of P species are 4 N _{0} and that of Q are N_{0}. Half-life of P (for conversion to R) is 1 minute where as that of Q is 2 minutes. Initially there are no nuclei of R present in the sample. When number of nuclei of P and Q are equal, the number of nuclei of R present in the sample would be (Mains 2011)**

(a) 2 N_{0}

(b) 3 N_{0
}(c) 9N_{0}/2

(d) 5N_{0}/2

**28. Out of the following which one is not a possible energy for a photon to be emitted by hydrogen atom according to Bohr’s atomic model? (Mains 2011)**

(a) 0.65 eV

(b) 1.9 eV

(c) 11.1 eV

(d) 13.6 eV

**29. The mass of a ^{7}_{3}Li nucleus is 0.042 u less than the sum of the masses of all its nucleons. The binding energy per nucleon of ^{7}_{3}Li nucleus is nearly (Prelims 2010)**

(a) 46MeV

(b) 5.6 MeV

(c) 3.9 MeV

(d) 23 MeV

**30. The activity of a radioactive sample is measured as N _{0} counts per minute at t = 0 and N_{0}/e counts per minute at t = 5 The time (in minutes) at which the activity reduces to half its value is (Prelims 2010 )**

**31. The energy of a hydrogen atom in the ground state is -13.6 eV. The energy of a He**^{+}** ion in the first excited state will be (Prelims 2010 )**

(a) -13.6 eV

(b) -27.2 eV

(c) -54.4 eV

(d) -6.8 eV

**32. An alpha nucleus of energy 1/2 mv² bombards a heavy nuclear-target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to**

(a) 1/Ze

(b) v^{2}

(c) 1/m

(d) 1/v^{4}

**33. The decay constant of a radio isotope is λ. If A _{1}_{ }and A_{2} are its activities at times t_{1 }and t_{2 }respectively, the number of nuclei which have decayed during the time (t_{1} – t_{2}) (Mains 2010 )**

**34. The binding energy per nucleon in deuterium and helium nuclei are 1.1 MeV and 7.0 MeV, respectively. When two deuterium nuclei fuse to form a helium nucleus the energy released in the fusion is ( Mains 2010)**

(a) 23.6 MeV

(b) 2.2 MeV

(c) 28.0 MeV

(d) 30.2 MeV

**35. In the nuclear decay given below**

**the particles emitted in the sequence are (Prelims 2009, 1993)**

(a) γ, β, α

(b) β, γ, α

(c) α, β, γ

(d) β, α, γ

**36. The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an (Prelims 2009)**

(a) isomer of parent

(b) isotone of parent

(c) isotope of parent

(d) isobar of parent

**37. In a Rutherford scattering experiment when a projectile of charge z _{1} and mass M_{1} approaches a target nucleus of charge z_{2} and mass M_{2}, the distance of closest approach is r_{0}. The energy of the projectile is (Prelims 2009)**

(a) directly proportional to z_{1}z_{2} .

(b) inversely proportional to z_{1}

(c) directly proportional to mass M_{1}

(d) directly proportional to M_{1} x M_{2}

**38. The ionization energy of the electron in the hydrogen atom in its ground state is 13.6 eV. The atoms are excited to higher energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between (Prelims 2009)**

(a) n = 3 to n = 1 states

(b) n = 2 to n = 1 states

(c) n = 4 to n = 3 states

(d) n = 3 to n – 2 states

**39. If M(A; Z), M _{p} and M_{n} denote the masses of the nucleus ^{A}_{Z}X, proton and neutron respectively in units of u (1 u = 931.5 MeV/c^{2}) and BE represents its bonding energy in MeV, then (Prelims 2008)**

**40. Two nuclei have their mass numbers in the ratio of 1 : 3. The ratio of their nuclear densities would be (Prelims 2008)**

(a) (3)^{1/3}: 1

(b) 1:1

(c) 1:3

(d) 3:1

**41. The ground state energy of hydrogen atom is -13.6 eV. When its electron is in the first excited state, its excitation energy is (Prelims 2008)**

(a) 10.2 eV

(b) 0

(c) 3.4 eV

(d) 6.8 eV

**42. Two radioactive materials X _{1} and X_{2} have decay constants 5λ and λ respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of X_{1} to that X_{2} will be 1/e after a time (Prelims 2008)**

(a) 1/4λ.

(b) e/λ

(c) λ

(d) 1/2 λ

**43. Two radioactive substances A and B have decay constants 5λ and λ respectively. At t = 0 they have the same number of nuclei. The ratio of number of nuclei of A to those of B will be (1/e) ^{2} after a time interval**

(a) 4λ

(b) 2λ

(c) 1/2 λ

(d) 1/4 λ

**44. In a radioactive decay process, the negatively charged emitted β-particles are (2007)**

(a) the electrons produced as a result of the decay of neutrons inside the nucleus

(b) the electrons produced as a result of collisions between atoms

(c) the electrons orbiting around the nucleus

(d) the electrons present inside the nucleus.

**45. In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular paths of radius R using a magnetic field If V and B are kept constant, the charge on the ion ratio will be proportional to mass of the ion (2007)**

(a) 1 /R^{2}

(b) R^{2
}(c) R

(d) 1/R.

**46. A nucleus has mass represented by M (A, Z). If M _{p} and M_{n} denote the mass of proton and neutron respectively and B.E. the binding energy in MeV, then (2007)**

**47. If the nucleus ^{27}_{13}Al has a nuclear radius of about 3.6 fm, then ^{125}_{32}Te would have its radius approximately as (2007)**

(a) 9.6 fin

(b) 12.0 fm

(c) 4.8 fin

(d) 6.0 fm.

**48. The total energy of electron in the ground state of hydrogen atom is -13.6 eV. The kinetic energy of an electron in the first excited state is (2007)**

(a) 6.8 eV

(b) 13.6 eV

(c) 1.7 eV

(d) 3.4 eV.

**49. Ionization potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. According to Bohr’s theory, the spectral lines emitted by hydrogen will be (2006)**

(a) one

(b) two

(c) three

(d) four.

**50. In a radioactive material the activity at time t _{1 }is R_{1} and at a later time t_{2}, it is R_{2}. If the decay constant of the material is λ, then (2006)**

**51. The binding energy of deuteron is 2.2 MeV and that of 2 He is 28 MeV. If two deuterons are fused to form one ^{4} He then the energy released is (2006)**

(a) 30.2 MeV

(b) 25.8 MeV

(c) 23.6 MeV

(d) 19.2 MeV.

**52. The radius of germanium (Ge) nuclide is measured to be twice the radius of ^{9}_{4}Be. The number of nucleons in Ge are (2006)**

(a) 72

(b) 73

(c) 74

(d) 75.

**53. In the reaction**

** **

** if the binding energies of ^{2}_{1}H, ^{3}_{1}H and ^{4}_{2}He are respectively a, b and c (in MeV), then the energy (in MeV) released in this reaction is (2005)**

(a) a + b + c

(b) a + b – c

(c) c- a – b

(d) c + a – b.

**54. The total energy of an electron in the first excited state of hydrogen atom is about – 3.4 eV. Its kinetic energy in this state is**

(a) 3.4 eV

(b) 6.8 eV

(c) – 3.4 eV

(d) – 6.8 eV. (2005)

**55. Which one of the following pairs of nuclei are isotones? (2005)**

**56. In any fission process the ratio**

(a) equal to 1

(b) greater than 1

(c) less than 1

(d) depends on the mass of the parent nucleus.

**57. Energy levels A, B and C of a certain atom corresponding to increasing values of energy e. E _{a} < E_{B} < E_{c}. If λ_{1}, λ_{2} and λ_{3} are wavelengths of radiations corresponding to transitions C to B, B to A and C to A respectively, which of the following relations is correct? (2005, 1990)**

**58. Fission of nuclei is possible because the binding energy per nucleon in them (2005)**

(a) increases with mass number at low mass i numbers

(b) decreases with mass number at low mass j numbers

(c) increases with mass number at high mass i numbers

(d) decreases with mass number at high massj numbers.

**59. A nucleus represented by the symbol has (2004)**

(a) Z neutroils and A – Z protons I

(b) Z protons and A – Z neutrons

(c) Z protons and A neutrons

(d) A protons and Z – A neutrons

**60. If in a nuclear fusion process the masses of the fusing nuclei be m _{x} and m_{2} and the mass of the resultant nucleus be m_{}}, then**

(a) m_{3} = m_{1} + m_{2}

(b) m_{3} = |m_{1} – m_{2}|

(c) m_{3} < (m_{1} + m_{2})

(d) m_{3} > (m_{1} + m_{2})

**61. model of atoms (2004)**

(a) Assumes that the angular momentum of electrons is quantized.

(b) Uses Einstein’s photoelectric equation.

(c) Predicts continuous emission spectra for atoms.

(d) Predicts the same emission spectra for all types of atoms.

**62. The half life of radium is about 1600 Of 100 g of radium existing now, 25 g will remain unchanged after (2004)**

(a) 4800 years

(b) 6400 years

(c) 2400 years

(d) 3200 years

**63. M _{p} denotes the mass of a proton and M_{n} that of a neutron. A given nucleus, of binding energy B, contains Z protons and N The mass M (N, Z) of the nucleus is given by (where c is the velocity of light)**

**64. An electron is moving round the nucleus of a hydrogen atom in a circular orbit of radius The Coulomb force F between the two is**

**65. Solar energy is mainly caused due to**

(a) burning of hydrogen in the oxygen

(b) fission of uranium present in the Sun

(c) fusion of protons during synthesis of heavier elements

(d) gravitational contraction (2003)

**66. The volume occupied by an atom is greater than the volume of the nucleus by a factor of about (2003)**

(a) 10

(b) 10^{5
}(c) 10^{10}

(d) 10^{15}

**67. A sample of radioactive element has a mass of 10 g at an instant t = 0. The approximate mass of this element in the sample after two mean lives is (2003)**

(a) 35 g

(b) 2.50 g

(c) 3.70 g

(d) 6.30 g

**68. In which of the following systems will the radius of the first orbit (n = 1) be minimum ? (2003)**

(a) doubly ionized lithium

(b) singly ionized helium

(c) deuterium atom

(d) hydrogen atom

**69. The mass of proton is 1.0073 u and that of neutron is 1.0087 u (u = atomic mass unit). The binding energy of ^{4}_{2}He is (Given helium nucleus mass = 4.0015 u.) (2003)**

(a) 0.0305 J

(b) 0.0305 erg

(c) 28.4 MeV

(d) 0.061 u

**70. The mass number of a nucleus is (2003)**

(a) always less than its atomic number

(b) always more than its atomic number

(c) sometimes equal to its atomic number

(d) sometimes less than and sometimes more than its atomic number

**71. A nuclear reaction given by represents (2003)**

(a) β-decay

(b) γ-decay

(c) fusion

(d) fission

**72. Which of the following are suitable for the fusion process? (2002)**

(a) light nuclei

(b) heavy nuclei

(c) element lying in the middle of the periodic table.

(d) middle elements, which are lying on binding energy curve.

**73. A sample of radioactive element containing 4 x 10 ^{16} active nuclei. Half life of element is 10 days, then number of decayed nuclei after 30 days (2002)**

(a) 0.5 x 10^{16}

(b) 2 x 10^{16
}(c) 3.5 x 10^{16}

(d) 1 x 10^{16}.

**74. A deutron is bombarded on _{8}O^{16} nucleus then α-particle is emitted. The product nucleus is (2002)**

**75. Which rays contain (positive) charged particles? (2001)**

(a) α-rays

(b) β-rays

(c) γ-rays

(d) X-rays.

**76. X(n, α) ^{7}_{3}Li, then X will be**

**77. Half life of a radioactive element is 12.5 hour and its quantity is 256 g. After how much time its quantity will remain 1 g? (2001)**

(a) 50 hrs

(b) 100 hrs

(c) 150 hrs

(d) 200 hrs.

**78. The interplanar distance in a crystal is 2.8 x 10 ^{-8} The value of maximum wavelength which can be diffracted (2001)**

(a) 8 x 10^{-8} m

(b) 5.6 x 10^{-8 }m

(c) 1.4 x 10^{-8 }m

(d) 7.6 x 10^{-8 }m.

**79. The energy of hydrogen atom in n ^{th} orbit is E„ then the energy in n^{th} orbit of singly ionised helium atom will be (2001)**

(a) 4E_{n}

(b) E_{n}/4

(c) 2E_{n}

(d) E_{n}/2.

**80. M _{n} and M_{p} represent the mass of neutron and proton respectively. An element having mass M has N neutrons and Z protons, then the correct relation will be**

**81. Energy released in nuclear fission is due to (2001)**

(a) some mass is converted into energy

(b) total binding energy of fragments is more than the binding energy of parental element

(c) total binding energy of fragments is less than the binding energy of parental element

(d) total binding energy of fragments is equal to the binding energy of parental element.

**82. For the given reaction, the particle X is (2000)**

(a) neutron

(b) anti neutrino

(c) neutrino

(d) proton.

**83. Maximum frequency of emission is obtained for the transition (2000)**

(a) n = 2 to n = 1

(b) n = 6 to n = 2

(c) n = 1 to n = 2

(d) n = 2 to n = 6.

**84. The relation between λ and T _{1/2} as (T_{1/2} —» half life)**

**85. Nuclear fission is best explained by (2000)**

(a) liquid droplet theory

(b) Yukawa π-meson theory

(c) independent particle model of the nucleus

(d) proton-proton

**86. The life span of atomic hydrogen is (2000)**

(a) fraction of one second

(b) one year

(c) one hour

(d) one

**87. When an electron does transition from n = 4 to n = 2, then emitted line spectrum will be (2000)**

(a) first line of Lyman series

(b) second line of Balmer series

(c) first line of Paschen series

(d) second line of Paschen series.

**88. Alpha particles are (1999)**

(a) neutrally charged

(b) positron

(c) protons

(d) ionized helium atoms

**89. After lα and 2β-emissions (1999)**

(a) mass number reduces by 6

(b) mass number reduces by 4

(c) mass number reduces by 2

(d) atomic number remains unchanged

**90. Complete the equation for the following fission process**

**91. A nucleus _{n}X^{m} emits one α and two β particles. The resulting nucleus is (1998)**

**92. Atomic weight of Boron is 10.81 and it has two isotopes _{5}B^{10} and _{5}B^{n}. Then the ratio of _{5}B^{10} : _{5}B^{u} in nature would be (1998)**

(a) 15: 16

(b) 10:11

(c) 19:81

(d) 81:19

**93. In the Bohr model of a hydrogen atom, the centripetal force is furnished by the coulomb attraction between the proton and the electron. If a _{0} is the radius of the ground state orbit, m is the mass and e is the charge on the electron and e_{0 }is the vacuum permittivity, the speed of the electron is**

**94. The 21 cm radiowave emitted by hydrogen in interstellar space is due to the interaction called the hyperfine interaction in atomic hydrogen. The energy of the emitted wave is nearly**

(a) 7 x 10^{-8} joule

(b) 1 joule

(c) 10^{-17} joule

(d) 10^{-14} joule

**95. Half-lives of two radioactive substances A and B are respectively 20 minutes and 40 minutes. Initially the samples of A and B have equal number of nuclei. After 80 minutes the ratio of remaining numbers of A and B nuclei is**

(a) 1 : 4

(b) 4 : 1

(c) 1 : 16

(d) 1 : 1

**96. Due to earth’s magnetic field, the charged cosmic rays particles**

(a) can never reach the pole

(b) can never reach the equator

(c) require greater kinetic energy to reach the equator than pole

(d) require less kinetic energy to reach the equator than pole.

**97. Which of the following is used as a moderator in nuclear reaction? (1997)**

(a) cadmium

(b) plutonium

(c) uranium

(d) heavy water.

**98. The energy of the ground electronic state of hydrogen atom is – 13.6 eV. The energy of the first excited state will be**

(a) – 27.2 eV

(b) -52.4eV

(c) – 3.4 eV

(d) – 6.8 eV.

**99. When hydrogen atom is in its first excited level, its radius is ………… of the Bohr radius. (1997)**

(a) twice

(b) 4 times

(c) same

(d) half.

**100. The most penetrating radiation out of the following are (1997)**

(a) β-rays

(b) γ-rays

(c) X-rays

(d) α-rays.

**101. The minimum wavelength of the X-rays produced by electrons accelerated through a potential difference of V volts is directly proportional to**

**102. The energy of a hydrogen atom in its ground state is – 13.6 eV. The energy of the level corresponding to the quantum number n = 2 in the hydrogen atom is (1996)**

(a) – 0.54 eV

(b) -3.4eV

(c) – 2.72 eV

(d) -0.85eV.

**103. According to Bohr’s principle, the relation between principal quantum number (n) and radius of orbit (r) is (1996)**

**104. A nucleus ruptures into two nuclear parts, which have their velocity ratio equal to 2 : 1. What will be the ratio of their nuclear size (nuclear radius)? (1996)**

**105. What is the respective number of α and β particles emitted in the following radioactive decay? (1995)**

**106. The binding energies per nucleon for a deuteron and an α-particle are x _{1} and x_{2} respectively. The energy Q released in the reaction **

**107. The count rate of a Geiger Muller counter for the radiation of a radioactive material of half-life of 30 minutes decreases to 5 second ^{-1} after 2 hours. The initial count rate was**

(a) 80 second^{-1}

(b) 625 second^{-1}^{
}(c) 20 second^{-1}

(d) 25 second^{-1}.

**108. An electron makes a transition from orbit n = 4 to the orbit n = 2 of a hydrogen atom. What is the wavelength of the emitted radiations? (R = Rydberg’s constant)**

**109. When a hydrogen atom is raised from the ground state to an excited state, (1995)**

(a) both K.E. and RE. increase

(b) both K..E. and RE. decrease

(c) the P.E. decreases and K.E. increases

(d) the RE. increases and K.E. decreases.

**110. The figure represents the observed intensity of X-rays emitted by an X-ray tube, as ^function of wave-length. The sharp peaks A and B denote (1995)**

(a) white radiations

(b) characteristic radiations

(c) band spectrum

(d) continuous spectrum

**111. The figure indicates the energy level diagram of an atom and the origin of six spectral lines in emission (e.g. line no. 5 arises from the transition from level B to A). Which of the following spectral lines will occur in the absorption spectrum? (1995)**

(a) 4,5,6

(b) 1,2, 3,4, 5,6

(c) 1,2,3

(d) 1,4,6.

**112. The mass number of He is 4 and that of sulphur i is 32. The radius of sulphur nucleus is larger than that of helium by the factor of (1995)**

(a) 4

(b) 2

(c) 8

(d) √8

**113. The binding energy per nucleon is maximum in case of**

(a) ^{4}_{2}He

(b) ^{56}_{26}Fe_{
}(c) ^{141}_{56}Ba

(d) ^{235}_{92}U

**114. Which source is associated with a line emission I spectrum? (1993)**

(a) Electric fire

(b) Neon street sign

(c) Red traffic light

(d) Sun

**115. Energy released in the fission of a single ^{235}_{92}U nucleus is 200 MeV. The fission rate of ^{235}_{92}U filled reactor operating at a power level of 5 W is**

**116. Hydrogen atoms are excited from ground state of the principle quantum number 4. Then the number of spectral lines observed will be (1993)**

(a) 3

(b) 6

(c) 5

(d) 2

**117. In terms of Bohr radius a _{0}, the radius of the second Bohr orbit of a hydrogen atom is given by**

**118. Solar energy is due to**

(a) fusion reaction

(b) fission reaction

(c) combustion reaction

(d) chemical reaction

**119. The ionization energy of hydrogen atom is 13.6 eV. Following Bohr’s theory, the energy corresponding to a transition between 3 ^{rd} and 4^{th }orbit is (1992)**

(a) 3.40 eV

(b) 1.51 eV

(c) 0.85 eV

(d) 0.66 eV

**120. The energy equivalent of one atomic mass unit is**

(a) 1.6 x 10 ^{-19} J

(b) 6.02 x 10^{23} J

(c) 931 MeV

(d) 9.31 MeV

**121. The mass of a-particle is (1992)**

(a) less than the sum of masses of two protons and two neutrons ‘

(b) equal to mass of four protons

(c) equal to mass of four neutrons

(d) equal to sum of masses of two protons and two neutrons

**122. Of the following pairs of species which one will have the same electronic configuration for both members? (1992)**

(a) Li^{+} and Na^{+}

(b) He and Ne^{+
}(c) H and Li

(d) C and N^{+}

**123. The mass density of a nucleus varies with mass number A as (1992)**

(a) A^{2}

(b) A

(c) constant

(d) 1/A

**124. The constituents of atomic nuclei are believed to be (1991)**

(a) neutrons and protons

(b) protons only

(c) electron and protons

(d) electrons, protons and neutrons

**125. The half life of radium is 1600 years The fraction of a sample of radium that would remain after 6400 years**

(a) 1/4

(b) 1/2

(c) 1/8

(d) 1/16

**126. In the nucleus of _{11}Na^{23}, the number of protons, neutrons and electrons are**

(a) 11,12,0

(b) 23,12, 11

(c) 12, 11,0

(d) 23,11,12

**127. The ground state energy of H-atom 13.6 eV. The energy needed to ionize H-atom from its second excited state (1991)**

(a) 1.51 eV

(b) 3.4 eV

(c) 13.6 eV

(d) none of these

**128. If the nuclear force between two protons, two neutrons and between proton and neutron is denoted by F _{pp}, F_{nn} and F_{pn} respectively, then**

**129. The valence electron in alkali metal is a (1990)**

(a) f-electron

(b) p-electron

(c) s-electron

(d) d-electron

**130. Consider an electron in the n ^{th} orbit of a hydrogen atom in the Bohr model. The circumference of the orbit can be expressed in terms of de Broglie wavelength λ of that electron as (1990)**

(a) (0.529)nλ

(b) √Nλ

(c) (13.6)λ

(d) nλ

**131. The nuclei _{6}C^{13} and _{7}N^{14} can be described^as (1990)**

(a) isotones

(b) isobars

(c) isotopes of carbon

(d) isotopes of nitrogen

**132. Which, of the folowing statements is true for nuclear forces? (1990)**

(a)They obey the inverse square law of distance.

(b) They obey the inverse third power law of distance.

(c) They are short range forces.

(d) they are equal in strength to electromagnetic forces.

**133. The ratio of the radii of the nuclei _{13}A1^{27} and _{52}Te^{125} approximately (1990)**

(a) 6 : 10

(b) 13 : 52

(c) 40:177

(d) 14:73

**134. The nucleus _{6}C^{12} absorbs an energetic neutron and emits a beta particle (p). The resulting nucleus is (1990)**

(a) _{7}N^{14}

(b) _{7}N^{13
}(c) _{5}B^{13}

(d) _{6}C^{13}

**135. A radioactive element has half life period 800 years. After 6400 years what amount will remain? (1989)**

(a) 1/2

(b) 1/16

(c) 1/8

(d) 1/256

**136. An element A decays into element C by a two step process**

Then

(a) A and C are isotopes

(b) A and C are isobars

(c) A and B are isotopes

(d) A and B are isobars (1989)

**137. Curie is a unit of (1989)**

(a) energy of gamma rays

(b) half-life

(c) radioactivity

(d) intensity of gamma rays

**138. The average binding energy of a nucleon inside an atomic nucleus is about (1989)**

(a) 8 MeV

(b) 8 eV

(c) 8 J

(d) 8 erg

**139. To explain his theory, Bohr used**

(a) conservation of linear momentum

(b) quantisation of angular momentum

(c) conservation of quantum frequency

(d) none of these (1989)

**140. The atomic number of silicon is 14. Its ground state electron configuration is (1989)**

**141. A radioactive sample with a half life of 1 month has the label : ‘Activity = 2 micro curies on 1 – 8 – 1991’. What would be its activity two months earlier? (1988)**

(a) 1.0 micro curie

(b) 0.5 micro curie

(c) 4 micro curie

(d) 8 micro curie

**142. The nucleus ^{115}_{48}Cd, after two successive β-decay will give (1988)**

**143. The ionisation energy of hydrogen atom is 13.6 eV, the ionisation energy of a singly ionised helium atom would be (1988)**

(a) 13.6 eV

(b) 27.2 eV

(c) 6.8 eV

(d) 54.4 eV

**ANSWERS**

**EXPLANATIONS**

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