CBSE Questions for Class 12 Medical Physics Atoms Quiz 7 - MCQExams.com

The gravitational attraction between electron and proton in a hydrogen atom is weaker than the coulomb attraction by a factor of about $$10^{-40}$$. An alternative way of looking at this fact is to estimate the radius of the first Bohr orbit of a hydrogen atom if the electron and proton were bound by gravitational attraction. You will find the answer interesting.
  •  The radius of the first Bohr orbit and the estimated size of the whole universe is same.
  •  The radius of the first Bohr orbit is much greater than the estimated size of the whole universe.
  •  The radius of the first Bohr orbit is much smaller than the estimated size of the whole universe.
  • None of the above.
Who gave the Quantum model of hydrogen atom ?
  • S.N. Bose
  • Niels Bohr
  • James clerk Maxwell
  • R. A. Millikan
Rutherford's alpha-particle scattering experiment was responsible for the discovery of:
  • atomic nucleus
  • electron
  • proton
  • neutron
Which of the following is not an inherent property of the photons?
  • Momentum
  • Energy
  • Charge
  • Velocity
The angular speed $$(\omega)$$ of an electron revolving in $$n^{th}$$ Bohr orbit and corresponding principal quantum number(n) are related as ____________.
  • $$\omega\propto n^3$$
  • $$\omega\propto\dfrac{1}{ n^3}$$
  • $$\omega\propto n^2$$
  • $$\omega\propto\dfrac{1}{ n^2}$$
The ionisation potential of hydrogen atom is -13.6 eV. An electron in the ground state of a hydrogen atoms absorb a photon of energy 12.75 eV. How many different spectral line can one expect when the electron make a downward transition?
  • 1
  • 4
  • 2
  • 6
If a cathode ray tube has a potential difference $$V$$ volt between the cathode and anode, then the speed $$v$$ of cathode rays is given by:
  • $$v\propto { V }^{ 2 }$$
  • $$v\propto \sqrt { V } $$
  • $$v\propto \cfrac { 1 }{ V } $$
  • $$v\propto V$$
If an electron is revolving around the hydrogen nucleus at a distance of $$0.1$$nm, what should be its speed?
  • $$2.188\times 10^6 ms^{-1}$$
  • $$1.094\times 10^6 ms^{-1}$$
  • $$4.376\times 10^6 ms^{-1}$$
  • $$1.59\times 10^6 ms^{-1}$$
In a hydrogen atom, the electron is making $$6.6\times 10^{15} revs^{-1}$$ around the nucleus in an orbit of radius $$0.528 \overset{o}{A}$$. The magnetic moment $$(A-m^2)$$ will be.
  • $$1\times 10^{-15}$$
  • $$1\times 10^{-10}$$
  • $$1\times 10^{-23}$$
  • $$1\times 10^{-27}$$
The spectrum obtained from the chromosphere of the sun at the time of total solar eclipse is :
  • line emission spectrum
  • band emission spectrum
  • continuous emission spectrum
  • line absorption spectrum
Which state of triply ionised Beryllium $$(Be^{+++})$$ has the same orbital radius as that of the ground state of hydrogen ?
  • $$n = 3$$
  • $$n = 4$$
  • $$n = 1$$
  • $$n = 2$$
Bohr's atom model assumes.
  • The nucleus is of infinite mass and is at rest
  • Electrons in a quantized orbit will not radiate energy
  • Mass of electron remains constant
  • All the above.
The difference between the wavelengths of the Stokes line and Anti-Stokes lines in the Raman spectrum of $$H-Br$$ molecule is $$100\mathring { A } $$. If the wavelength of the Anti-Stokes line is $$5000\mathring { A } $$ the wavelength of the incident radiation is:
  • $$5050 \mathring { A } $$
  • $$4950 \mathring { A } $$
  • $$5100 \mathring { A } $$
  • $$4900 \mathring { A } $$
Most of the $$\alpha$$-particles passed straight through the gold foil. This proved the existence of ________ in an atom.
  • electrons
  • nucleus
  • empty space
  • positive charge
If elements with principal quantum number $$n>4$$ were not allowed in nature, the number of possible elements would have been:
  • $$32$$
  • $$60$$
  • $$64$$
  • $$4$$
Which of the following is not a conclusion of Rutherford experiment?
  • An atom has a very small compact nucleus
  • An atom is mainly empty space
  • An atom's mass is concentrated in the nucleus
  • An atom has a very dense nucleus
  • An atom has a negatively charged nucleus
For the Paschen series the values of $${ n }_{ 1 }$$ and $${ n }_{ 2 }$$ in the expression $$\Delta E=Rhc\left( \dfrac { 1 }{ { n }_{ 1 }^{ 2 } } -\dfrac { 1 }{ { n }_{ 2 }^{ 2 } }  \right) $$ are
  • $${ n }_{ 1 }=1,{ n }_{ 2 }=2,3,4,\dots $$
  • $${ n }_{ 1 }=2,{ n }_{ 2 }=3,4,5,\dots $$
  • $${ n }_{ 1 }=3,{ n }_{ 2 }=4,5,6,\dots $$
  • $${ n }_{ 1 }=4,{ n }_{ 2 }=5,6,7,\dots $$
Which of the following was not a conclusion of Rutherford's gold foil experiment?
  • The atom is mainly empty space.
  • The nucleus has a negative charge.
  • The atom has a dense nucleus.
  • Alpha particles can pass through a thin sheet of gold foil.
  • All of the above are correct regarding the gold foil experiment.
Statement I: Rutherford in his experiment observed that, most of the alpha particles passed straight through a thin sheet of gold foil.
Statement II: Most of the space inside the atom is empty.
  • Both statements I and II are true.
  • Statement I is true and statement II is false.
  • Statement I is false and statement II is true.
  • Both statement I and II are false.
  • Ambiguous
For absorption and emission spectra of atoms which one of the following particle changes energy levels?
  • Alpha
  • Electron
  • Neutron
  • Photon
  • Proton
$$_{ 95 }^{ 241 }{ Am }\ \rightarrow \ _{ 93 }^{ 237 }{ Np }+Y$$
In the above nuclear fusion reaction, Identify the particle represented by $$Y$$?
  • A proton
  • An electron
  • An alpha particle
  • A gamma ray
  • A beta particle
Which of the following statement is true on a scattering of atom according to Rutherfords experiments on the alpha particle ?
  • Atoms are roughly spherical with a radius of about $${10}^{-10} m$$
  • The electrons occupy quantized energy levels, absorbing or emitting energy only when they make a quantum jump between these levels
  • The density of positive charge within an atom is not uniform throughout the atoms volume
  • Allowed electron orbits must have a circumference equal to a whole number times the electrons de Broglie wavelength
  • Alpha particles are positively charged
Statement 1: A large number of alpha particles were deflected in the Rutherford experiment.
Statement 2: Alpha particles that came close to the nucleus were deflected.

  • Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.

  • Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.

  • Statement 1 is correct but Statement 2 is not correct.

  • Statement 1 is not correct but Statement 2 is correct.

  • Both the Statement 1 and Statement 2 is not correct.

 Which of the following is true regarding atoms according to Rutherford's gold foil experiment?
  • Are mostly space
  • Are in continuous motion
  • Have negative orbitals
  • Have diffuse charge distribution
  • Have dense crystalline structure
According to Bohr's model of the atom, atoms emit or absorb radiation only at certain wavelengths.Identify why is it so
  • Because the protons and electrons are distributed evenly throughout the atom
  • Because electrons can orbit the nucleus at any radius
  • Because electrons orbit the nucleus only at certain discrete radii
  • Because protons orbit the nucleus only at certain discrete radii
  • Because photons can only have discrete wavelength
The discrete spectral lines of line spectra occur when excitation of electrons takes place in
  • Solids
  • Liquids
  • Gases
  • Plastics
  • All of these
Which of the following assumptions made by Neils Bohr regarding the hydrogen atom was NOT new and "radical"?
  • Electrons are only stable in certain orbits
  • Atoms only emit electromagnetic radiation when electrons transition to lower energy states
  • The Coulomb force is responsible for keeping the electron in orbit around the positive nucleus
  • An electron in a hydrogen atom can only orbit the nucleus if its angular momentum is some integer multiple of $$h/2 \pi$$
  • All of the above were new and "radical"
When a high energy (fast moving) electron approaches a heavy metal target, some of the electrons are significantly deflected by nuclei, and they lose much of their energy. This lost energy goes into the creation of high energy photons.
What process is being described here?
  • Compton scattering
  • The photoelectric effect
  • X-ray production
  • Pair production
  • Quantum tunneling
A high energy photon collides elastically with a charged particle (usually an electron)., The photon "bounces away" with less energy (a longer wavelength).
The process described here is known as :
  • Compton scattering
  • The photoelectric effect
  • X-ray production
  • Annihilation
  • Quantum tunneling
Rutherford's theory assumed which of the following paths for the electron?
  • Elliptical
  • Circular
  • Spiral
  • All the above
Rutherford's experiment on scattering of $$\alpha$$-particles showed for the first time that the atom has
  • Nucleus
  • Electron
  • Proton
  • Neutron
A beam of alpha-particles is fired at a piece of gold foil as shown in the image. After striking the gold foil in which direction do most of the alpha-particles travel?
517390_d0e67460910d4e2b8ea0e98e55850cab.png
  • $$P$$
  • $$Q$$
  • $$R$$
  • $$S$$
Which of the following observations of $$\alpha$$-ray scattering experiment lead to the presence of small positively charged nucleus in the centre?
  • Most of the $$\alpha$$-particles passed straight
  • Most of the $$\alpha$$-particles rebounded after hitting the atoms
  • Only a few $$\alpha$$-particles deflected away from their path
  • Very few $$\alpha$$-particles rebounded
Rutherford's experiment for the first time proved that an atom has:
  • protons
  • a nucleus
  • neutrons
  • electrons
As one considers orbits with higher values of n in a hydrogen atom, the electric potential energy of the atom
  • decreases
  • increases
  • remains the same
  • does not increase.
In which of the following transitions will the wavelength be minimum ?
  • $$n = 5$$ to $$n = 4$$
  • $$n = 4$$ to $$n = 3$$
  • $$n = 3$$ to $$n = 2$$
  • $$n = 2$$ to $$n = 1.$$
Total energy of electron in an excited state of hydrogen atom is $$-3.4 eV$$. The kinetic and potential energy of electron in this state
  • $$K=-3.4 eV$$ $$U=-6.8 eV$$
  • $$K=3.4 eV$$ $$U=-6.8 eV$$
  • $$K=-6.8 eV$$ $$U=+3.4 eV$$
  • $$K=+10.2 eV$$ $$U=-13.6 eV$$
An electron with kinetic energy 5 eV is incident on a hydrogen atom in its ground state. The collision
  • must be elastic
  • may be partially elastic
  • must be completely inelastic
  • may be completely inelastic.
When a photon stimulates the emission of another photon, the two photons have
  • same energy
  • same direction
  • same phase
  • same wavelength.
If $$E_P$$ and $$E_k$$ represent potential energy and kinetic energy respectively, of an orbital electron, then according to Bohr's theory:
  • $$E_k= -E_p/2$$
  • $$E_k= -E_p$$
  • $$E_k= -2E_p$$
  • $$E_k= 2E_p$$
Which of the following spectral series of hydrogen atom is lying in visible range of electromagnetic wave?
  • Paschen series
  • Pfund series
  • Lyman series
  • Balmer series
When electron jumps from $$n=4$$ level to $$n=1$$ level, the angular momentum of electron changes by
  • $$\dfrac{h}{2\pi}$$
  • $$\dfrac{2h}{2\pi}$$
  • $$\dfrac{3h}{2\pi}$$
  • $$\dfrac{4h}{2\pi}$$
White light is passed through sodium vapours contained in a thin walled glass flask and the transmitted light is examined with the help of a spectrometer. The spectrum so obtained is.
  • Absorption spectrum
  • Solar spectrum
  • Band spectrum
  • Continuous spectrum
If the minimum energy of photons needed to produce photoelectric effect is 3eV, bombarding the photoelectric material by a number of photons of 2.5eV also one can get
  • photoelectrons of the same kinetic energy
  • photoelectrons of the higher kinetic energy
  • higher current
  • none
When a beam of white light is passed through sodium vapours and then through a spectrometer, spectrum so obtained has two dark lines present in the yellow region. This spectrum is called
  • band spectrum
  • continuous spectrum
  • absorption spectrum of sodium
  • emission spectrum of sodium
 In the hydrogen atom an electron is moving in nth orbit. The circumference s of the orbit and the de Broglie wavelength, of the moving electron are related by the equation
  • $$S=n \lambda$$
  • $$S=\dfrac{\lambda}{n}$$
  • $$S=\dfrac{n}{\lambda}$$
  • None of these
When electron in hydrogen atom jumps from second orbit to first orbit, the wavelength of radiation emitted is $$\lambda$$. When electron jumps from third orbit to first orbit, the wavelength of emitted radiation would be 
  • $$\cfrac { 27 }{ 32 } \lambda $$
  • $$\cfrac { 32 }{ 27 } \lambda $$
  • $$\cfrac { 2 }{ 3 } \lambda $$
  • $$\cfrac { 3 }{ 2 } \lambda $$
Radius of the second Bohr orbit of a singly ionised helium atom is
  • $$0.53 A^o$$
  • $$1.06 A^o$$
  • $$0.265 A^o$$
  • $$0.132 A^o$$
The wave length of K-ray line of an anti cathode element of atomic number Z is nearly proportional to:
  • $$Z^2$$
  • $$(Z-1)^2$$
  • 1/(Z-1)
  • 1/$$(Z-1)^2$$
If the electron in the hydrogen atoms is excited to n = 5 state, the number of frequencies present in the radiation emitted is :
  • 4
  • 5
  • 8
  • 10
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