AIEEE - Atomic Nucleus - 1

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TARGET COURSE AIEEEDAILY PRACTICE PROBLEM SHEET

Batch : Target AIEEE Faculty : JJRJ Subject : Physics Date : Topic : Atomic Nucleus

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1. If 13.6 eV energy is required to ionize the hydrogen atom, then the required to remove an electron from n = 2 is a) 10.2 eV b) 0 eV c) 3.4 eV d) 6.8 eV

2. If N0 is the original mass of the substance of half-life period t1/2 = 5 years, then the amount of substance left after 15 years is a) N0/8 b) N0/16 c) N0 / 2 d) N0 / 4

3. Which of the following cannot be emitted by radioactive substances during their decay?a) Electrons b) Protons c) Neutrionoes d) Helium nuclei

4. A radioactive sample at any instant has its disintegration rate 5000 disintegrations per minute. After 5 minutes, the rate is 1250 disintegration per minute. Then, the decay constant (per minute ) is a) 0.8 ln 2 b) 0.4 ln 2 c) 0.2 ln 2 d) 0.1 ln 2

5. A nucleus with Z = 92 emits the following in a sequence : α, β–, β–, α, α, α, α, α, β–, β–, α, β+, β+, α,The Z of the resultant nucleus is a) 74 b) 76 c) 78 d) 82

6. Which of the following atoms has the lowest ionization potential ?

a) O b) N c) Cs d) Ar

7. The wavelengths involved in the spectrum of deuterium (

D) are slightly different from that of hydrogen spectrum,

becausea) the attraction between the electron and the nucleus is different in the two cases b) The size of the two nuclei are different c) the nuclear forces are different in the two cases d) the masses of the two nuclei are different.

8. In the nuclear fusion reaction H + H H + n, given

that the repulsive potential energy between the two nuclei is – 77 10–14 J, the temperature at which the gases must be heated to initiate the reaction is nearly [Boltzmann’s constant k = 1.38 10–23J/K]a) 109 K b) 107 K c) 105 K d) 103 K

9. If the binding energy of the electron in hydrogen atom is 13.6 eV, the energy required to remove the electron from the first excited state of Li is a) 122.4 eV b) 30.6 eV c) 13.6 eV d) 3.4 eV

10. A nucleus disintegrated into two nuclear parts which have their velocities in the ratio 2 : 1. The ratio of their nuclear sizes will be a) 21/3 : 1 b) 1 : 31/2 c) 31/2 : 1d) 1 : 21/3

11. The binding energy per nucleon of deuteron ( H) and

helium nucleus ( H)is 1.1MeV and 7 MeV respectively. If

two deutron nuclei react to form a single helium nucleus, then the energy released is

a) 13.9 MeV b) 26.9 MeVc) 23.6 MeV d) 19.2 MeV

12. An α-particle of energy 5 MeV is scattered through 180o by a fixed uranium nucleus. The distance of the closest approach is of the order of a) 1 Å b) 10–10cm c) 10–12 cm d) 10–15 cm

13. Starting with a sample of pure 66Cu, of it decays

into Zn in 15 minutes. The corresponding half-life is

a) minute b) 5 minutes

c) 15 minute d) 10 minute

14. If radius of the Al nucleus is estimated to be 3.6

Fermi then the radius of Te nucleus be nearly

a) 5 fermi b) 4 fermi c) 8 fermi d) 6 fermi

15. A nuclear transformation is denoted by X (n, α) Li.

Which of the following is the nucleus of element X?

a) Be b) B c) B d) 12C6

16. The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy?a) II b) I c) IV d) III

17. The intensity of gamma radiation from a given source

is I. On passing through 36 mm of lead, it is reduced to

. The thickness of lead which will reduce the intensity to

will be

a) 12 mm b) 18 mm c) 9 mm d) 6 mm

18. According to Bohr’s theory, the radius of orbit described by principal quantum number n and atomic number Z is proportional to a) Z2n2 b) Z2/n2 c) Z2/n d) n2/Z

19. The radius of Bohr’s first orbit is a0. The electron in the nth orbit has a radius a) na0 b) a0/n c) n2a0 d) a0/n2

20. As one considers orbits with higher values of n in a hydrogen atom, the electric potential energy of the atom a) decreases b) increases c) remains the same d) does not increase

21. The ratio between kinetic energy and total energy of the electron of hydrogen atom, according to Bohr’s model, is




a) 1 : – 1 b) 1 : 1 c) 1 : 2 d) 2 : 1

22. Two electrons in an atom are moving in orbits of radii R and 9R respectively. The ratio of their frequencies will be a) 1 : 8 b) 8 : 1 c) 1 : 27 d) 27 : 1

23. What amount of original radioactive atom is left after five half lives?a) 3 % b) 5 % c) 10 % d) 20 %

24. In radioactive decay, if N is the number of nuclei decaying in interval t and N is the number of mean active nuclei during that interval, the graph between the quantity r = (1/N) N/t versus time t will have the shape a) 1 b) 2 c) 3 d) 4

25. The activity of a radioactive sample is 1.6 curie and its half-life is 2.5 days. Its activity after 10 days will be a) 0.8 curie b) 0.4 curie c) 0.1 curie d) 0.16 curie

26. An energy level diagram for an atom is shown drawn to scale. The electron transitions give rise to the emission of a spectrum of lines of wavelength, λ1, λ2, γ3, λ4, λ5.Which statement is correct a) It can be deduced from the energy level diagram that λ1 > λ2.b) It can be deduced from the energy level diagram that λ3 = λ1 + λ5.c) Of the five wavelengths λ4 is the shortest. d) The transition corresponding to wavelength λ3 represents the ionization of the atom.

27. An electron has a mass of 9.1 10–31 kg. It revolves around the nucleus in a circular orbit of radius 0.529 10–10

metre at a speed of 2.2 106 ms–1. The magnitude of its linear momentum in this motion is a) 1.1 10–34 kg ms–1 b) 2.0 10–24 kg ms–1

c) 4.0 10–24 kg ms–1 d) 4.0 10–31 kg ms–1

28. A radioactive sample consists of two distinct species having equal number of atoms initially. The mean life time of one species is τ and that of the other is 5τ. The decay products in both cases are stable. A plot is made of the total number of radioactive nuclei as a function of time. Which of the following figures best represents the form of this plot?

29. Four lowest energy levels of H atom are shown in fig. The number of possible emission lines would be

a) 3 b) 4 c) 5 d) 6

30. The minimum wavelength of Paschen series of hydrogen atom will be a) 18700 Å b) 970 Å c) 1022 Å d) 8182 Å

31. The ratio of area of orbit of first excited state of electron to the area of orbit of ground level, for hydrogen atom, will be a) 16 : 1 b) 4 : 1 c) 8 : 1 d) 2 : 1

32. The maximum wavelength of Bracket series of hydrogen atom will be a) 404 Å b) 4040 Å c) 40404 Å d) 40400 Å

33. A hydrogen atom in the ground state is excited by radiations of wavelength 975 Å. The energy state to which the atom is excited, is a) 4 b) 3 c) 2 d) 1

34. The fraction of atoms of radioactive element that decays in 6 days is 7/8. The fraction that decays in 10 days will be a) 70/80 b) 77/88 c) 31/32 d) 35/36

35. The radius of the nucleus with nucleon number 2 is 1.5 10–15 m. Then the radius of nucleus with nucleon number 54 will be a) 4 10–15 m b) 4.5 10–15 m c) 5 10–15 m d) 5.5 10–15 m

36. Radiations of wavelength λ are incident on hydrogen atoms in the ground state. A fraction of these radiations is absorbed by these atoms. There are ten different wavelengths in the emission spectrum of excited atoms. The value of λ will be a) 1212 Å b) 912 Å c) 947 Å d) 1247 Å




37. If the half lives of a radioactive element for α and β decay are 4 year and 12 year respectively, then the percentage of the element that remains after 12 year will be a) 6.25 % b) 5.25% c) 4.25% d) 3.50

38. The ratio of magnetic moment of an electron to its angular momentum in an atomic orbit will be

a) b) c) d)

Answer 1. c2. a3. b4. b5. c6. c7. d8. a9. b10. d11. c12. c13. b14. d15. c16. b17. a18. d19. c20. c21. c22. c23. a24. c25. c26. a27. b28. d29. d30. d31. a32. d33. a34. c35. b36. c37. a38. c


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AIEEE - Atomic Nucleus - 1