CBSE Questions for Class 12 Medical Physics Atoms Quiz 1 - MCQExams.com

According to DE Broglie, wavelength of electron in second orbit is 10$$^{ -9 }$$ meter. Then the circumstances of orbit is :-
  • 10$$^{ -9 }$$ m
  • 2×10$$^{ -9 }$$m
  • 3×10$$^{ -9 }$$m
  • 4×10$$^{ -9 }$$m
In a H-atom, the transition takes place from L to K shell. If $$R=1.08\times {10}^{7}{m}^{-1}$$, the wave length of the light emitted is nearly
  • $$4400\mathring{A}$$
  • $$1250\mathring{A}$$
  • $$1650\mathring{A}$$
  • $$1850\mathring{A}$$
Which of the following particles cannot be deflected by magnetic field ?
  • Electrons
  • Neutrons
  • $$\alpha-$$ particles
  • Protons
In which of the following fields cathode rays show minimum deflection ?
  • Electric field
  • Magnetic field
  • Plasma field
  • Gravitational field
How will you relate velocity of cathode rays to c, if ‘c' denotes the velocity of light?
  • Equal to c
  • Greater than c
  • Less than c
  • Either greater or less than c
Anti-particle of proton is
  • Electron
  • Antiproton
  • Positron
  • Neutron
If the K.E. of a cathode ray beam is 8KeV, then the tube should work at a Potential Difference of
  • 4 KV
  • 8 KV
  • 8 V
  • 4 V
On decreasing principal quantum number $$n$$, the value of $$r$$ will :
  • decrease
  • increase
  • remain the same
  • none of the above
Who proposed the planetary model of the atom?
  • Earnest Rutherford
  • Max Planck
  • Neils Bohr
  • James Chadwick
  • J.J. Thompson
In Rutherford experiment, most of the alpha particles go straight through the foil because________
  • Alpha particles are much heavier than electron.
  • Alpha particles are positively charged.
  • Alpha particles move with high velocity.
  • Most part of the atom is empty.
In terms of Bohr radius $${a}_{0}$$, the radius of the second Bohr orbit of a hydrogen atom is given by:
  • $$8{a}_{0}$$
  • $$4{a}_{0}$$
  • $$2{a}_{0}$$
  • $$\sqrt {2}{a}_{0}$$
The photon radiated from hydrogen corresponding to $$2nd$$ line of Lyman series is absorbed by a hydrogen like atom $$'X'$$ in $$2nd$$ excited state. As a result the hydrogen like atom $$'X'$$ makes a transition to $$n^{th}$$ orbit. Then,
  • $$X=He^+, n=4$$
  • $$X=Li^{++}, n=6$$
  • $$X=He^+, n=6$$
  • $$X=Li^{++}, n=9$$
The hydrogen atom in ground state is excited by a monochromatic radiation of $$  \lambda=975 A^{\circ}  $$ . Number of spectral lines in the resulting spectrum emitted will be
  • 3
  • 2
  • 6
  • 10
An excited electron of H-atoms emits a photon of wavelength λ and returns in the ground state, the principal quantum number of excited state is given by:
  • $$\sqrt{ [(λR-1)/(λR)]}$$
  • $$\sqrt{ [(λR)/(λR-1)]}$$
  • $$\sqrt{ [λR(λR-1)]}$$
  • $$λR(R-1)$$
The radius of which of the following orbit is same as that of the first Bohr's orbit of hydrogen atom 
  • $${ He }^{ + }(n=2)$$
  • $${ Li }^{ 2+ }(n=2)$$
  • $${ Li }^{ 2+ }(n=3)$$
  • $$\ { Be }^{ 3+ }(n=2)$$
If $$\lambda_{max.} = 6563 \dot{A}$$ , then wavelength of second line for Balmer series will be :
  • $$\lambda = \dfrac{16}{3 R}$$
  • $$\lambda = \dfrac{36}{5 R}$$
  • $$\lambda = \dfrac{4}{3 R}$$
  • none of these
The relation between $${\lambda}_{1}$$: wavelength of series limit of Lyman series, $${\lambda}_{0}$$: the wavelength of the series limit of Balmer series and $${\lambda}_{3}$$: the wavelength of first line of Lyman series is:
  • $${\lambda}_{1}={\lambda}_{2}+{\lambda}_{3}$$
  • $${\lambda}_{3}={\lambda}_{1}+{\lambda}_{2}$$
  • $${\lambda}_{2}={\lambda}_{3}+{\lambda}_{1}$$
  • None of these
The magnetic field at the center of a hydrogen atom due to the motion of electron varies with the principal quantum number as
  • $$n^{5}$$
  • $$n^{3}$$
  • $$1/n^{5}$$
  • $$1/n^{3}$$
According to bohr model, the diameter of first orbit of hydrogen atom will approximately be
  • $$1$$$$A^{0}$$
  • $$0.529$$$$A^{0}$$
  • $$2.25$$$$A^{0}$$
  • $$0.725$$$$A^{0}$$
How can the brightness of the pattern on the screen or cathode ray tube be changed ?
  • By changing the negative potential on grid.
  • By changing the positive potential on grid.
  • We can't increase the brightness
  • None of the above
According to kinetic theory of matter, a molecule is the smallest particle of a substance and it possesses :
  • all the properties of the substance
  • some of the properties of the substance
  • none of the properties of the substance
  • both a and b are true
The time by a photo-electron to come out after the photon strikes is approximately 
  • $$10^{-1}s$$
  • $$10^{-4}s$$
  • $$10^{-10}s$$
  • $$10^{-16}s$$
According to Bohr's theory, the time averaged magnetic field at the centre (i.e nucleus) of a bydrogen atom due to the motion of electrons in the $$n^{th}$$ orbit is propotional to : $$(n =$$ principal quantum number$$)$$
  • $$n^{-3}$$
  • $$n^{-4}$$
  • $$n^{-5}$$
  • $$n^{-2}$$
The graph which depicts the results of Rutherford gold foil experiment with $$\alpha$$-particles is:
$$\theta$$ : Scattering angle
$$Y$$ : Number of scattered $$\alpha$$-particles detected
(Plots are schematic and not to scale)
The transition from the state $$n = 4$$ to $$n = 3$$ in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from
  • $$2\rightarrow 1$$
  • $$3\rightarrow 2$$
  • $$4\rightarrow 2$$
  • $$5\rightarrow 4$$.
The acceleration of an electron in the first orbit of the hydrogen atom $$(n =1)$$ is : 
  • $$\dfrac{h^2}{\pi^2m^2r^3}$$
  • $$\dfrac{h^2}{8\pi^2m^2r^3}$$
  • $$\dfrac{h^2}{4\pi m^2r^3}$$
  • $$\dfrac {2\pi^2kme^2Z}{\eta h}$$
A diatomic molecule has moment of inertia $$I$$. By Bohrs quantization condition its rotational energy in the $$n^{th}$$ level ($$n = 0$$ is not allowed) is
  • $$\displaystyle \frac{1}{\mathrm{n}^{2}}(\frac{\mathrm{h}^{2}}{8\pi^{2}\mathrm{I}})$$
  • $$\displaystyle \frac{1}{\mathrm{n}}(\frac{\mathrm{h}^{2}}{8\pi^{2}\mathrm{I}})$$
  • $$\displaystyle \mathrm{n}(\frac{\mathrm{h}^{2}}{8\pi^{2}\mathrm{I}})$$
  • $$\displaystyle \mathrm{n}^{2}(\frac{\mathrm{h}^{2}}{8\pi^{2}\mathrm{I}})$$
In a $$\mathrm{C}\mathrm{O}$$ molecule, the distance between $$\mathrm{C}$$ (mass $$=12$$ a.m.u) and $$\mathrm{O}$$ (mass $$=16$$ a.m.u.), where 1 a.m.u $$=\displaystyle \frac{5}{3}\times 10^{-27} kg,$$ is close to 
  • $$2.4\times 10^{-10}\mathrm{m}$$
  • $$1.9\times 10^{-10}\mathrm{m}$$
  • $$1.3\times 10^{-10}\mathrm{m}$$
  • $$4.4\times 10^{-11}\mathrm{m}$$
 The electric potential between a proton and an electron is given by  $$V=\displaystyle \mathrm{V}_{0}\ln\frac{\mathrm{r}}{\mathrm{r}_{0}}$$ , where $$\mathrm{r}_{0}$$ is a constant. Assuming Bohr's model to be applicable, write variation of $$\mathrm{r}_{\mathrm{n}}$$ with $$\mathrm{n},\ \mathrm{n}$$ being the principal quantum number?
  • $$\mathrm{r}_{\mathrm{n}}\propto \mathrm{n}$$
  • $$\mathrm{r}_{\mathrm{n}}\propto 1/\mathrm{n}$$
  • $$\mathrm{r}_{\mathrm{n}}\propto \mathrm{n}^{2}$$
  • $$\mathrm{r}_{\mathrm{n}}\propto 1/\mathrm{n}^{2}$$
Match the appropriate pairs from Lists I and II:
List-IList - II
a) Nitrogen moleculee) Continuous spectrum
b) Incandescent solidsf) Absorption spectrum
c) Fraunhofer linesg) Band spectrum
d) Electric arc between iron rodsh) Emission spectrum
  • a-g, b-e, c-f, d-h
  • a-f, b-e, c-h, d-g
  • a-h, b-e, c-f, d-g
  • a-e, b-g, c-h, d-f
The electrostatic energy of $$Z$$ protons uniformly distributed throughout a spherical nucleus of radius $$R$$ is given by
$$\displaystyle E=\frac { 3 }{ 5 } \frac { Z\left( Z-1 \right) { e }^{ 2 } }{ 4\pi { \varepsilon  }_{ 0 }R } $$
The measured masses of the neutron, $$\displaystyle _{ 1 }^{ 1 }{ H },\, _{ 7 }^{ 15 }{ N }$$ and $$\displaystyle _{ 8 }^{ 15 }{ O }$$ are $$1.008665\  u, 1.007825 \ u, 15.000109\  u$$ and $$15.003065\  u$$, respectively. Given that the radii of both the $$\displaystyle _{ 7 }^{ 15 }{ N }$$ and $$\displaystyle _{ 8 }^{ 15 }{ O }$$ nuclei are same, $$\displaystyle 1u=931.5\quad { MeV }/{ { c }^{ 2 } }$$ (c is the speed of light) and $$\displaystyle { { e }^{ 2 } }/{ \left( 4\pi { \varepsilon  }_{ 0 } \right)  }=1.44\,MeV\,fm$$. Assuming that the difference between the binding energies of $$\displaystyle _{ 7 }^{ 15 }{ N }$$ and $$\displaystyle _{ 8 }^{ 15 }{ O }$$ is purely due to the electrostatic energy, the radius of either of the nuclei is $$(1\, fm = 10^{-15}m)$$:
  • $$2.85\  fm$$
  • $$3.03\  fm$$
  • $$3.42\  fm$$
  • $$3.80\  fm$$
For which one of the following, Bohr model is not valid?
  • Singly ionised helium atom $$(He^+)$$
  • Deuteron atom
  • Singly ionised neon atom $$(Ne^+)$$
  • Hydrogen atom
The value of Planck's constant is $$6.63\times 10^{-34}Js$$. The speed of light $$3\times 10^{17}\:nm\:s^{-1}$$. Which value is closest to the wavelength in nanometer of a quantum of light with frequency of $$6\times 10^{15}s^
{-1}$$?
  • $$10$$
  • $$25$$
  • $$50$$
  • $$75$$
  • Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
  • Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
  • Assertion is correct but Reason is incorrect.
  • Both Assertion and Reason are incorrect.
Whenever a stream of electrons collides with a stream of photons, in this collision, which of the following is not conserved?
  • Linear momentum
  • Total energy
  • No. of photons
  • No. of eletrons
What would be the radius of second orbit of $${He}^{+}$$ ion?
  • $$1.058\mathring { A } $$
  • $$3.023\mathring { A } $$
  • $$2.068\mathring { A } $$
  • $$4.458\mathring { A } $$
  1. According to Bohr's theory, the radius of the $$n^{th}$$ orbit of an atom of atomic number $$ Z$$ is proportional to 
  • $$\dfrac{n^2}{Z^2}$$
  • $$\dfrac{n^2}{Z}$$
  • $$\dfrac{n}{Z}$$
  • $$n^2Z^2$$
Consider the following two statements A and B and identify the correct choice in the given answers
A) Line spectra is due to atoms in gaseous state
B) Band spectra is due to molecules 
  • Both A and B are false
  • A is true but B is false
  • A is false but B is true
  • Both A and B are true.
Match the following :
List - 1 List - 2
a) Burning candlee) line spectrum
b) Sodium vapourf) continuous spectrum
c) Bunsen flameg) bond spectrum
g) Dark lines in solar spectrum h) Absorption spectrum
  • a-g, b-e, c-f, d- h
  • a- g, b-f, c-e, d-h
  • a-f, b-g, c-e, d-h
  • a-f, b-e, c-g, d-h
An incandescent filament emits a spectrum which is :
  • line spectrum
  • band spectrum
  • continuous spectrum
  • characteristic spectrum
Light from a tungsten filament lamp gives
  • Absorption spectrum
  • Emission spectrum
  • Atomic spectrum
  • Discontinuous spectrum
Check the wrong statement :
  • Line spectrum is characteristic of the element
  • Absorption line spectrum is characteristic of the element
  • Continuous spectrum is characteristic of the source of light
  • There are two prominent yellow lines in the spectrum of sodium
Solar spectrum is an example of 
  • line emission spectrum
  • band absorption spectrum
  • line absorption spectrum
  • continuous emission spectrum
Which of the following scientists developed the nuclear model of the atom ?
  • John Dalton 
  • Robert Milikan 
  • Henry Moseley
  • Ernest Rutherford
The spectra used to identify the elements in the mixture is :
  • Emission
  • Absorption
  • Emission and Absorption
  • Molecular spectrum
The element which was observed in solar spectrum is 
  • Helium
  • Xenon
  • Neon
  • Argon
The rest mass of a photon is
  • zero
  • $$1.6\times 10^{-19}kg$$
  • $$3.1\times 10^{-30}kg$$
  • $$9.1\times 10^{-31}kg$$
Bohrs atomic model assumes :
  • the nucleus is of infinite mass and is at rest
  • electron in a quantized orbit will not radiate energy
  • mass of the electron remains constant
  • all of the above
The incorrect statement from the following is:
  • Material wave (de-Broglie wave) can travel in vacuum.
  • Electromagnetic wave can travel through vacuum.
  • The velocity of photon is the same as light passes through any medium.
  • Wavelength of de-Broglie wave depends upon velocity.
The particle that possesses half integral spin is
  • Photon
  • Pion
  • Proton
  • K-meson
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