Atomic and Nuclear Physics Quiz | objective questions | Physics General Knowledge Questions | MCQ

Atomic and Nuclear Physics Quiz | objective questions | Physics General Knowledge Questions | MCQ

"1 >>According to ‘plum pudding model’ atoms on the whole are electrically neutral because ?

• (A) the positive charge of the atom is uniformly distributed throughout the volume of the atom and the negatively charged electrons are embedded in it
• (B) the positive charge of the atom is uniformly distributed throughout the volume of the electron and the negative charge of electrons balances positive parts
• (C) the negative charge of the atom is uniformly distributed throughout the volume of the atom and the positively charged electrons are embedded in it
• (D) positive charge is concentrated at one place and negative charge is elsewhere.

Solution According to ‘plum pudding model’ atoms on the whole are electrically neutral because the positive charge of the atom is uniformly distributed throughout the volume of the atom and the negatively charged electrons are embedded in it

2 >>Each element is associated with ?

• (A) with a characteristic absorption of monochromatic light
• (B) with a characteristic radiation of monochromatic light
• (C) no light radiation or absorption
• (D) with a characteristic spectrum of radiation

Solution Each element is associated with with a characteristic spectrum of radiation

3 >>alpha particles used in Geiger-Marsden experiment were obtained from ?

• (A) accelerating He ions
• (B) accelerating H ions
• (C) electron accelerators
• (D) Bi²¹⁴ Radioactive source

Solution alpha particles used in Geiger-Marsden experiment were obtained from Bi214 Radioactive source

4 >>In Geiger-Marsden experiment very small deflection of the beam was expected because ?

• (A) positive charge and the negative electrons are distributed through the whole atom reducing electric field inside the atom
• (B) there are no electrical forces at work
• (C) particles are collimated by lead screens
• (D) most particles pass through

Solution In Geiger-Marsden experiment very small deflection of the beam was expected because positive charge and the negative electrons are distributed through the whole atom reducing electric field inside the atom

5 >>Which of these statements correctly describe the atomic model according to classical electromagnetic theory ? ?

• (A) the positive charge and negative electron cancel and no waves are radiated
• (B) The waves emitted by electrons are discrete
• (C) The electrons would spiral inwards and fall into the nucleus
• (D) electrons do not radiate electromagnetic waves

Solution In classical electromagnetic theory, atoms and molecules are considered to contain electrical charges (i.e. electrons, ions) which are regarded as oscillating about positions of equilibrium, each with its appropriate natural frequency, vo . When placed in a radiation field of frequency v , each oscillator in the atom or molecule is set into forced vibration with the same frequency as that of the radiation. The amplitude of the forced vibration is small, but as v approaches vo , the amplitude of the forced vibration increases rapidly. To account for the absorption of energy from the radiation field, it is necessary to assume that the oscillator in the atom or molecule must overcome some frictional force proportional to its velocity during its forced motion. For small amplitudes of forced oscillation, the frictional force, and therefore the absorption of energy, is negligible. Near resonance , the amplitude of oscillation becomes large, with a correspondingly large absorption of energy to overcome the frictional force. Therefore, the radiation of frequencies near the natural frequency of the oscillator corresponds to an absorption band.

6 >>In Geiger-Marsden experiment prediction was that ?

• (A) some particles would be expected at 45^∘
• (B) All the particles would go through the foil with hardly any deflection
• (C) some particles would be expected at 75^∘
• (D) All the particles would bounce from the foil at 180^∘

Solution In Geiger-Marsden experiment prediction was that All the particles would go through the foil with hardly any deflection

7 >>In Geiger-Marsden experiment, at the point of closest approach ?

• (A) the kinetic energy is zero and the electrical potential equals the initial kinetic energy supplied
• (B) the kinetic energy is not zero and the electrical potential equals the initial kinetic energy supplied
• (C) the kinetic energy is not zero and the electrical potential is less than the initial kinetic energy supplied
• (D) the kinetic energy is not zero and the electrical potential is greater than the initial kinetic energy supplied

Solution In Geiger-Marsden experiment, at the point of closest approach the kinetic energy is zero and the electrical potential equals the initial kinetic energy supplied

8 >>In Geiger-Marsden experiment, actual results was ?

• (A) Number of particles at angle ϕ was zero at ϕ =80^o
• (B) Number of particles at angle ϕ was zero at ϕ =180^o
• (C) Number of particles at angle ϕ was zero at ϕ =70^o
• (D) Number of particles at angle ϕ was non zero at all angles including at 180^o

Solution In Geiger-Marsden experiment, actual results was Number of particles at angle ϕ was non zero at all angles including at 180o

9 >>The model that best explains the results of Geiger-Marsden experiment is ?

• (A) Bohr model
• (B) None of the above
• (C) Rutherford model
• (D) Thomson model

Solution The model that best explains the results of Geiger-Marsden experiment is Rutherford model

10 >>A Spectrum is ?

• (A) The splitting into the component colors of white light when passed through a prism or a diffraction grating
• (B) The splitting into the component colors or wavelengths of light when passed through a lens.
• (C) the splitting into the component colors or wavelengths of monochromatic light when passed through a prism or a diffraction grating
• (D) The splitting into the component colors or wavelengths of light when passed through a prism or a diffraction grating

Solution A Spectrum is splitting of light into the component colors or wavelengths of light when passed through a prism or a diffraction grating

11 >>Continuous spectrum is produced by ?

• (A) Hydrogen atoms in magnetic field
• (B) incandescent lamp
• (C) Hydrogen atoms in electrical field
• (D) lasers

Solution an emission spectrum that consists of a continuum of wavelengths.

12 >>Emission line spectrum of atoms contains ?

• (A) All colors of visible light without sharp boundaries
• (B) All colors in the form of isolated sharp parallel lines generally produced by heated resistances
• (C) Only a few colors in the form of isolated sharp parallel lines generally produced by heated gases
• (D) Only a few colors in the form of isolated sharp parallel lines generally produced by chilled gases

Solution a spectrum of the electromagnetic radiation emitted by a source.

13 >>Absorption line spectrum is obtained ?

• (A) If we pass off-white (discrete-spectrum) light through a hot gas
• (B) If we pass white (continuous-spectrum) light through a cool gas
• (C) If we pass white (continuous-spectrum) light through a hot gas
• (D) If we pass off-white (discrete-spectrum) light through a cool gas

Solution a spectrum of electromagnetic radiation transmitted through a substance, showing dark lines or bands due to absorption at specific wavelengths.

14 >>To produce an emission spectrum of hydrogen ?

• (A) It needs to be cool liquid form
• (B) It needs to be hot and white light shining through
• (C) It needs to be cold and white light shining through
• (D) It needs to be in glowing gaseous form

Solution To produce an emission spectrum of hydrogen It needs to be in glowing gaseous form

15 >>The half life of radium is 1600 years. The fraction of a sample of radium that would remain undecayed after 6400 years is ?

• (A) (1/4)
• (B) (1/2)
• (C) (1/8)
• (D) 41290

Solution a) After 1600yrs - 0.5 decayed, 0.5 left After 3200 yrs - there's 0.5 left, so you need to take half of that, i.e. a further 0.25 of the initial sample would have decayed. so total decayed = 0.75, total undecayed = 0.25 After 4800 - half of the 0.25 left will decayed, i.e. a further 0.125 of initial sample will decay. so total decayed = 0.75 + 0.125 = 0.875 of initial sample = 7/8 b) 6400 yrs is a further half life (from part a). After 4800 yrs, 1/8 is left, so after another half life, 1/16 will be left

16 >>Emission line spectra of different elements ?

• (A) is not different
• (B) is the same if both elements are in liquid form
• (C) is the same if both elements are at the same temperature
• (D) is different

Solution Emission line spectra of different elements is different

17 >>Which of these statements about Bohr model is correct? ?

• (A) Bohr model combines classical and early quantum concepts
• (B) Bohr model postulates wavy paths around the nucleus
• (C) Bohr model is based classical electromagnetic theory
• (D) Bohr model is pure quantum mechanical theory

Solution Bohr model combines classical and early quantum concepts

18 >>Which of these statements about Bohr model hypothesis is correct? ?

• (A) mass of electron is quantized
• (B) angular momentum of electron is quantized
• (C) radius of electron is quantized
• (D) velocity of electron is quantized

Solution angular momentum of electron is quantized is hypothesis in bohr's model

19 >>Which of these statements about De Broglie Explanation of Bohr model is correct? ?

• (A) Standing wave is formed on a circular orbit where integral number of de Broglie wavelengths fit into the circumference of the orbit
• (B) electron in its circular orbit, as proposed by Bohr, must be seen as electromagnetic wave
• (C) electron in its circular orbit, as proposed by Bohr, must be seen as a particle .
• (D) travelling wave is formed on a circular orbit where integral number of de Broglie Wavelengths fit into the circumference of the orbit

Solution Standing wave is formed on a circular orbit where integral number of de Broglie wavelengths fit into the circumference of the orbit is correct Debroglie statement

20 >>Fluorescence is ?

• (A) it consists only of atoms going into stable excited states
• (B) it consists of accelerated atoms/molecules striking suitable material
• (C) it consists of a molecule, atom or nanostructure relaxing to its ground state by emitting a photon of light after being excited to a higher quantum state by some type of energy
• (D) what happens in a fluorescent lamp

Solution Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation.

"21 >>Reason why there are many lines in an atomic spectrum is because ?

• (A) All atoms are in the same excited state and make transition to different states
• (B) All atoms are in the same excited state and make transition to same state
• (C) There are many atoms in different states of excitation making transition to different states
• (D) There are many atoms in different states of excitation making transition to the same state

Solution Reason why there are many lines in an atomic spectrum is because There are many atoms in different states of excitation making transition to different states

22 >>Fluorescent lamps are more efficient than incandescent lamps in converting electrical energy to visible light because ?

• (A) they do not waste as much energy producing (invisible) infrared photons
• (B) they produce more white light
• (C) they do not waste as much energy producing visible photons
• (D) they do not use uv radiations

Solution Fluorescent lamps are more efficient than incandescent lamps in converting electrical energy to visible light because they do not waste as much energy producing visible photons

23 >>According to Bohr model radiation takes place when ?

• (A) there is transition from one of the unstable orbits of definite energy to another of same energy
• (B) there is transition from one of the stable orbits of definite energy to another of lower energy.
• (C) there is transition from one of the unstable orbits of definite energy to another of higher energy
• (D) there is transition from one of the stable orbits of definite energy to another of higher energy

Solution According to Bohr model radiation takes place when there is transition from one of the unstable orbits of definite energy to another of same energy

24 >>According to Bohr model allowed values of angular momentum are ?

• (A) integral multiples of h
• (B) integral multiples of h/2(\pie)
• (C) integral multiples of h/(/pie)
• (D) continuous

Solution According to Bohr model allowed values of angular momentum are integral multiples of h/2(\pie)

25 >>In a Geiger -Marsden experiment, what is the distance of closest approach d to the nucleus of a 7.7 MeV α−particle before it comes momentarily to rest and reverses its direction? ?

• (A) 40 fm
• (B) 30 fm
• (C) 35 fm
• (D) 45 fm

Solution Use direct formula

26 >>Bandwidth of an electronic communication system ?

• (A) is the frequency range over which an equipment operates or the portion of the spectrum occupied by the signal
• (B) is the maximum frequency at which an equipment
• (C) is the minimum frequency at which an equipment
• (D) is number of bands in the spectrum

Solution Bandwidth of an electronic communication system is the frequency range over which an equipment operates or the portion of the spectrum occupied by the signal

27 >>As the mass number A increases, which of the following quantities related to a nucleus does not change? ?

• (A) density
• (B) volume
• (C) mass
• (D) binding energy

Solution As the mass number A increases, density of a nucleus does not change

28 >>A system has two charges qA=2.5×10⁻⁷C and qB=−2.5×10⁻⁷C located at points A: (0, 0, –15 cm) and B: (0,0, +15 cm), respectively. What are the total charge and electric dipole moment of the system? ?

• (A) zero, 7.5×10⁻⁸Cm
• (B) zero, 8.5×10⁻⁸Cm
• (C) zero, 6.5×10⁻⁸Cm
• (D) zero, 5.5×10⁻⁸Cm

Solution use direct formula

29 >>To produce N – type crystal Ge or Si may be doped with a substance that is ?

• (A) trivalent
• (B) divalent
• (C) pentavalent
• (D) tetravalent

Solution To produce N – type crystal Ge or Si may be doped with a substance that is pentavalent

30 >>Domestic power supply in India is ?

• (A) 230 V 50 Hz
• (B) 110 V 60 Hz
• (C) 416 V 60 Hz
• (D) 24 V DC

Solution Domestic power supply in India is 230V 50 Hz

31 >>What is the shortest wavelength present in the Paschen series of spectral lines? ?

• (A) 820 nm
• (B) 800 nm
• (C) 840 nm
• (D) 860 nm

Solution Theory based question

32 >>Suppose you are given a chance to repeat the alpha-particle scattering experiment using a thin sheet of solid hydrogen in place of the gold foil. (Hydrogen is a solid at temperatures below 14 K.) What results do you expect? ?

• (A) there would be scattering at 180
• (B) there would be scattering at 90
• (C) there would be scattering at all angles
• (D) there would be no scattering

Solution Suppose you are given a chance to repeat the alpha-particle scattering experiment using a thin sheet of solid hydrogen in place of the gold foil. (Hydrogen is a solid at temperatures below 14 K.) .there would be scattering at 180 is the result

33 >>In comparison to atomic size in Rutherford’s model, the size of the atom in Thomson’s model is ?

• (A) no different
• (B) slightly less
• (C) much less
• (D) much greater

Solution Rutherford's model did not completely reimagine Thomson's. Like Thomson,Rutherford still believed that atoms contained negatively charged electrons. Unlike the plum pudding model, where those atoms simply floated in soup, Rutherfordbelieved they orbited the central nucleus just as planets orbit the sun.

34 >>In the ground state of which model electrons are in stable equilibrium with zero net force? ?

• (A) No model
• (B) Rutherford’s model
• (C) Bohr model
• (D) Thomson’s model

Solution In the ground state of Thomson model model electrons are in stable equilibrium with zero net force

35 >>According to which model a classical atom is doomed to collapse? ?

• (A) Bohr model
• (B) Rutherford’s model
• (C) Thomson’s model
• (D) No model

Solution According to Rutherford model a classical atom is doomed to collapse

36 >>In which of the models An atom has a nearly continuous mass distribution? ?

• (A) Bohr model
• (B) Thomson’s model
• (C) Rutherford’s model
• (D) No model

Solution In Thomson models An atom has a nearly continuous mass distribution

37 >>In which of the models An atom has a highly non-uniform mass distribution? ?

• (A) No model
• (B) Thomson’s model
• (C) Bohr model
• (D) Rutherford’s model

Solution In Rutherford models An atom has a highly non-uniform mass distribution

38 >>In which of the models, the positively charged part of the atom possesses most of the mass? ?

• (A) Bohr model only
• (B) Thomson’s model only
• (C) Rutherford’s model only
• (D) Thomson’s model and Rutherford’s model

Solution In Thomson’s model and Rutherford’s models, the positively charged part of the atom possesses most of the mass

39 >>The ground state energy of hydrogen atom is –13.6 eV. What are the kinetic and potential energies of the electron in this state? ?

• (A) 13.1 eV, –29.2 eV
• (B) 14.6 eV, –29.2 eV
• (C) 13.6 eV, –27.2 eV
• (D) 14.6 eV, –27.2 eV

Solution kinetic energy is the negative of total energy. K.E. = -E also P.E. is equal to negative of two time of total energy. P.E.=-2E

40 >>A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. What series of wavelengths will be emitted? ?

• (A) Lyman series: 153 nm and 125 nm; Balmer series: 556 nm
• (B) Lyman series: 133 nm and 123 nm; Balmer series: 656 nm
• (C) Lyman series: 103 nm and 122 nm; Balmer series: 656 nm.
• (D) Lyman series: 143 nm and 122 nm; Balmer series: 646 nm

Solution In ground state, energy of gaseous hydrogen at room tempertaure= - 13.6 eV. When bombarded with 12.5 eV electron beam, the energy becomes, -13.6 +12.5 = -1.1 eV i.e. electron would jump from n=1 to n=3 where E 3= -13.6/3*3 = -1.5 eV On de-excitation the electron may jump from either n=3 to n=2 givind rise to Balmer series It may also jump from n = 3 to n =1 , giving rise to Lyman series

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