12th Class Physics Atomic Physics Question Bank

done Atoms Conceptual Problems Total Questions - 31

• question_answer1)
  Why Thomson's model of the atom is known as a plum pudding model?
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• question_answer2)
  Why did Thomson's atomic model fail?
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• question_answer3)
  Write two important inferences drawn from Rutherford's alpha particle scattering experiment.
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• question_answer4)
  Why do we use a very thin gold foil in Rutherford's \[\alpha \]-particle scattering experiment?
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• question_answer5)
  Why is it that mass of the nucleus does not enter the formula for impact parameter, but its charge does?
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• question_answer6)
  The kinetic energy of a-particle incident on gold foil is doubled. How does the distance of closest approach change?                    
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• question_answer7)
  The large angle scattering is possible only due to nucleus. Why?
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• question_answer8)
  The Rutherford \[\alpha \]-particle scattering experiment shows that most of the \[\alpha \]-particles pass through almost unscattered while some of them are scattered through large angles. What information does it give about the structure of atom?      
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• question_answer9)
  Why is electron revolving round the nucleus of an atom?                                               
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• question_answer10)
  In the Rutherford scattering experiment the distance of closest approach for an \[\alpha \]-particle is \[{{d}_{0}}\].If \[\alpha \]-particle is replaced by a proton, how much kinetic energy in comparison to \[\alpha \]-particle will it require to have the same distance of closest approach \[{{d}_{0}}\]?                                                    
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• question_answer11)
  What is the significance of the negative energy of electron in the orbit?         
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• question_answer12)
  What are stationary orbits?
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• question_answer13)
  State Bohr's quantisation condition in terms of de-Broglie wavelength.                      
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• question_answer14)
  State Bohr's postulate of quantization of aneular momentum of the orbiting electron in hydrogen atom.                        
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• question_answer15)
  When an electron falls from a higher energy to a lower energy level, the difference in the energies appears in the form of electro-magnetic radiation. Why cannot it be emitted as other forms of energy? 
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• question_answer16)
  Consider two different hydrogen atoms. The electron in each atom is in an excited state. Is it possible for the electrons to have different energies, but the same orbital angular momentum according to the Bohr model?                                     
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• question_answer17)
  With increasing quantum number, state whether the energy difference between adjacent levels increases or decreases?
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• question_answer18)
  How much is the energy possessed by an electron for \[n=\infty \]?
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• question_answer19)
  In a hydrogen atom, if the electron is replaced by a particle which is 200 times heavier but has the same charge, how would its radius change?           
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• question_answer20)
  The short wavelength limits of the Lyman, Paschen and Balmer series, in the hydrogen spectrum, are denoted by \[{{\lambda }_{L}},{{\lambda }_{P}}\]and \[{{\lambda }_{B}}\] respectively. Arrange these wavelengths in increasing order.
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• question_answer21)
  Find the ratio of energies of photons produced due to transition of an electron of hydrogen atom from its (i) second permitted energy level to the first level, and (ii) the highest permitted energy level to the first permitted level.                
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• question_answer22)
  Calculate the ratio of energies of photons produced due to transition of electron of hydrogen atom from its, (ii) second permitted energy level to the first level, and (ii) highest permitted energy level to the second permitted level. 
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• question_answer23)
  In the Rutherford's nuclear model of the atom, the nucleus (radius about \[{{10}^{-15}}\text{m}\]) is analogous to the sun about which the electrons move in orbit (radius \[\approx {{10}^{-10}}\text{m}\]) like the earth orbits around the sun. If the dimensions of the solar system had the same proportions as those of the atom, would the earth be closer to or farther away from the sun than actually it is? The radius of earth orbit is about\[~\mathbf{1}.\mathbf{5}\text{ }\times \text{ }\mathbf{1}{{\mathbf{0}}^{\mathbf{11}.}}\mathbf{m}\]. The radius of sun is taken as\[\mathbf{7\times 1}{{\mathbf{0}}^{\mathbf{8}}}\mathbf{m}\]                    
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• question_answer24)
  The trajectories, traced by different \[\alpha \]-particles, in Geiger-Marsden experiment were observed as shown in Fig. What names are given to the symbols \['b'\] and \['\upsilon '\] shown here? What can we say about the values of \['b'\] for (i) \[\theta \simeq 0\overset{\circ }{\mathop{\text{A}}}\,\] and (ii) \[\theta \simeq \pi \]radians?                
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• question_answer25)
  A beam of monoenergetic photons of energy \[\mathbf{9}\text{ }\mathbf{eV}\] is incident on a hydrogen gas containing all atoms in ground state. It is found that the beam is fully transmitted without absorption. Why?           
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• question_answer26)
  Explain why the spectrum of hydrogen atom has many lines, although a hydrogen atom contains only one electron.
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• question_answer27)
  Derive the expression for the radius of the \[\mathbf{nth}\] orbit of hydrogen atom using Bohr's postulates. Show graphically the (nature of) variation of the radius of orbit with the principal quantum number, n.
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• question_answer28)
  (a) Using Bohr's second postulate of quantization of orbital angular momentum, show that the circumference of the electron in the \[nth\] orbital state in hydrogen atom is \[n\] times the de-Broglie wavelength associated with it. (b) The electron in hydrogen atom is initially in the third excited state. What is the maximum number of spectral lines which can be emitted when it finally moves to the ground state?                                  
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• question_answer29)
  The energy of the electron in the ground state of hydrogen atom is -\[\mathbf{13}.\mathbf{6}\text{ }\mathbf{eV}.\] (i) What does the negative sign signify? (ii) How much energy is required to take an electron in this atom from the ground state to the first excited state?          
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• question_answer30)
  (a) The energy levels of an atom are as shown below. Which of them will result in the transition of a photon of wavelength 275 nm?   (b) Which transition corresponds to emission of radiation of (i) maximum wavelength and (ii) minimum wavelength?
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• question_answer31)
  Photons, with a continuous range of frequencies, are made to pass through a simple of rarefied hydrogen. The transitions, shown in Fig. indicate three of the spectral absorption lines in the continuous spectrum. (i) Identify the spectral series, of the hydrogen emission spectrum, to which each of these three lines correspond. (ii) Which of these lines corresponds to the absorption of radiation of maximum wavelength?                                   
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