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CBSE Questions for Class 12 Medical Physics Atoms Quiz 15 - MCQExams.com

According to the Bohr's theory of hydrogen atom, the speed of the electron, its energy and the radius of its orbit varies with the principal quantum number n, respectively, as:
  • 1n,1n2,n2
  • 1n,n2,1n2
  • n2,1n2,n2
  • n,1n,1n2
In Rutherford experiments on α- ray scattering the number of particles scattered at 90o be 28 per minute. Then the number of particles scattered per minute by the same foil, but at 60o is
  • 56
  • 112
  • 60
  • 120
If the radius of Bohr's second orbit of hydrogen atom is α then the radius of the 4th Bohr orbit in atom with Z=3, is
  • 4α3
  • 16α3
  • α4
  • None of these
The de Broglie wavelength of an electron in nth Bohr orbit of radius an(a0 being the first orbit radius):
  • 2πa0
  • 2πn2a0
  • 2πna0
  • 2πa0n

Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be :




  • 6
  • 2
  • 3
  • 5
The radius of the first orbit of hydrogen atom is equal to the radius of the
  • first orbit of He+
  • second orbit of Be3+
  • fourth orbit of He+
  • third orbit of Be3+
A particle of mass m moves in a circular orbit in a central potential field U(r)=12kr2. If Bohr's quantization condition is applied, radii of possible orbitals and energy levels vary with quantum number n as:
  • rnn2,En1n2
  • rnn,En1n
  • rnn,Enn
  • rnn,Enn
Mean free path of gas molecule at constant temperature is inversely proportional to 
  • P
  • V
  • m
  • n (number density)
If element with principal quantum number n>4 were not allowed in nature, then the number of possible elements would be 
  • 60
  • 32
  • 4
  • 64
The wavelength of second line of Balmer series is 4815 ˚A. The wavelength of first line Balmer series in the same atom is 
  • 4000 ˚A
  • 5000 ˚A
  • 6500˚A
  • 7500 ˚A
The ratio of the largest to shortest wavelength in Lyman series of hydrogen spectra is
  • 259
  • 176
  • 95
  • 43
A hydrogen atom, initially in the ground state is excited by absorbing a photon of wavelength 980˚A. The radius of the atom in excited state, in terms of Bohr radius a, will be:
(hc=12500eV˚A)
  • 4a0
  • 16a0
  • 9a0
  • None of these
The time taken by the electron in one complete revolution in the nth Bohr's orbit of the hydrogen atom is 
  • Inversely proportional to n2
  • Directly proportional to n3
  • Directly proportional to h2π
  • Inversely proportional to nh
When a silver foil (Z=47) was used in an α -ray scattering experiment, the number of α -particles scattered at 30o was found to be 200 per minute. If the silver foil is replaced by aluminium (Z=13) foil of the same thickness. The number of α -particles scattered per minute at 30o is nearly equal to
  • 15
  • 30
  • 10
  • 20
The radius of the orbital of electron in the hydrogen atom is 0.5A0 . the speed of the electron is 2×105m/s. then, the current in the loop due to the motion of the electron is 
  • 1 mA
  • 1.5 mA
  • 2.5 mA
  • 1.5×102mA
In hydrogen atom electron is revolving around nucleus in circular orbit with frequency of 6.57×115 revolutions. If its equivalent magnetic moment is 9.24×1024Am2 , the radius of orbit of electron is 

  • 0.27 A
  • 0.53 A
  • 1.27 A
  • 1.34 A
According to the Bohr theory of the hydrogen atom electrons starting in the 4th energy level and eventually ending in the ground state could produce a total of how many lines in the hydrogen spectra ?
  • 7
  • 6
  • 5
  • 4
Heat treatment of muscular pain involves radiation of wavelength of about 900 nm. Which spectral line H-atom is suitable for this purpose ?
Given: RH=1×105cm,h=6.61034Js,C=3×104m/s1 
  • Paschen 53
  • Paschen 3
  • Lyman, 1
  • Balmer 2
An αparticle when accelerated through a potential difference of V volt has a wavelength λ associated with it. In order to have same λ, by what potential difference a proton must be accelerated?
  • 8 V
  • 6 V
  • 4 V
  • 12 V
In an atom two electrons move round the nucleus in circular orbits of radii R and 4R respectively. The ratio of the time taken by them to complete one revolution is?
  • 14
  • 41
  • 81
  • 18
Which of following is not a conclusion of Rutherford's atomic model?
  • Most of the part inside an atom is empty.
  • Almost all mass of an atom is concentrated in the nucleus.
  • The size of nucleus is very small in comparison to the size fo atom.
  • Electron revolves round the nucleus in definite orbits.
In hydrogen atom, electron revolves around nucleus in circular orbit of radius 5×1011m at a speed 2.2×106m/s. Then the orbital current will be: 
  • 3.2 mA
  • 2.42 mA
  • 1.12 mA
  • 0.02 ma
 An electron of energy 150eV has wavelength of 1010m. The wavelength of a 60keV electron is
  • 5pm
  • 2pm
  • 12pm
  • 4pm
The ratio of frequencies of the first line of the lyman series and the first line of blamer series is 
  • 275
  • 278
  • 827
  • 427
Hydrogen atoms in a sample are excited to n=5 state and it is found that photons of all possible wavelengths are present in the emission spectra. The minimum number of hydrogen atoms in the sample would be
  • 5
  • 6
  • 10
  • infinite
The radius of the shortest orbit in a  one-electron system is 18 pm. It may be
  • hydrogen
  • deuterium
  • He+
  • Li++
The Bohr model for the spectra of a H- atom
  • will not be applicable to hydrogen in the molecular from.
  • Will not be applicable for a He - atom
  • is valid only at room tempreture.
  • predicts continuous as well as discrete spectral lines.
Assertion : According to classical theory, the proposed path of an electron in Rutherford atom model will be parabolic.
Reason : According to electromagnetic theory an accelerated particle continuously emits radiation. 
  • If both assertion and reason are true and the reason is the explanation of the assertion.
  • If both assertion and reason are true but reason is not the explanation of the assertion.
  • If assertion is true but reason is false.
  • If the assertion and reason both are false.
  • If assertion is false but reason is true.
The figure shows a graph between ln|AnA1| and 1n|n| where An is the area enclosed by the nth orbit in a hydrogen like atom. The correct curve is
1819276_b68246e8a335480586785fbfaae83926.png
  • 4
  • 3
  • 2
  • 1
0:0:1


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