CBSE Questions for Class 12 Medical Physics Atoms Quiz 10 - MCQExams.com

When $$_{90}Th^{238}$$ changes into $$_{83}Bi^{222}$$, then the number of emitted $$\alpha$$ and $$\beta$$ particles are ?
  • $$8\alpha,7\beta$$
  • $$4\alpha,7\beta$$
  • $$4\alpha,4\beta$$
  • $$4\alpha,1\beta$$
The quantum number corresponding to orbit of diameter 0.0001 mm in hydrogen atom will be nearly (Given that the radius of orbit with n = 1 is $$0.51\times 10^{-10}$$):
  • 39
  • 31
  • 9
  • 49
It is observed that some of the spectral lines in hydrogen spectrum have wavelengths almost equal to those of the spectral lines in $${ H }e^{ + }$$  ion, Out of the following the transitions in $${ H }e^{ + }$$ that will make this is :
  • $$n = 3$$ to $$n = 1 $$
  • $$n = 6$$ to $$n = 4 $$
  • $$n = 5$$ to $$n = 3$$
  • $$n = 3$$ to $$n = 2$$
The radius of the first Bohr orbit of a hydrogen atom is $$ 0.53\times 10^{-10}m$$.When an electron collides with this atom which is in its normal state, the radius of the electron orbit in the atom change to $$2.12 \times 10^{10}m$$.The value of the principal quantum number $$n$$ of the state to which it is excited is:
  • $$4$$
  • $$3$$
  • $$2$$
  • $$1$$
If energy required to remove one of the two electron from $$\text { He }$$ atom is $$29.5 eV,$$ then what is the value of energy required to convert a helium atom into $$\alpha -$$particle?
  • $$54.4eV$$
  • $$83.9eV$$
  • $$29.5eV$$
  • $$24.9eV$$
If an electron in a hydrogen atom has moved from $$n = 1$$  to  $$n = 10$$ orbit, the potential energy of the system has:
  • increased
  • decreased
  • remained unchanged
  • become zero
When light emitted by a white hot solid is passed through a sodium flame, the spectrum of the emergent light will show
  • The $$D_{1}$$ and $$D_{2}$$ bright yellow lines of sodium
  • Two dark lines in the yellow region
  • All colours from violet to red
  • No colours at all
The ratio of the speed of the electron in the first Bohr orbit of hydrogen and the speed of light is equal to then (where e, h and c have their usual meanings)
  • $$\dfrac{e^{12}}{2C\epsilon^{h}}$$
  • $$\dfrac{e^{2}}{2C\epsilon^{h}}$$
  • $$\dfrac{e^{3}}{2C\epsilon^{h}}$$
  • $$\dfrac{e^{4}}{2C\epsilon^{h}}$$
The ratio of the velocity of an electron in the first  Bohr's orbit of the hydrogen atom and the velocity of light is:
  • $$1:100$$
  • $$1:137$$
  • $$1:1000$$
  • $$1:10$$
How many times does the electron go round the first Bohr orbit in a second?
  • $$6.57 \times 10 ^ { 5 }$$
  • $$6.57 \times 10 ^ { 10 }$$
  • $$6.57 \times 10 ^ { 13 }$$
  • $$6.57 \times 10 ^ { 15 }$$
Photoelectric effect was successfully explained by 
  • Planck
  • Hallwash
  • Hertz
  • Einstein
Which of the following postulates of the Bohr model led to the quantization of energy of the hydrogen atom?
  • The electron goes around the nucleus in circular orbits.
  • The angular momentum of the electron can only be an integral multiple of $$h/2\pi$$.
  • The magnitude of the linear momentum of the electron is quantized
  • Quantization of energy is itself a postulate of the Bohr model.
a diatomic has a moment of inertia.By Bohr's quantization condition its rotational energy in the $$n^{th}$$ level ( n= 0 is not allowed ) is :
  • $$\frac{1}{n^{2}}\left ( \frac{h^{2}}{8\pi ^{2}I} \right )$$
  • $$\frac{1}{n}\left ( \frac{h^{2}}{8\pi ^{2}I} \right )$$
  • $$n\left ( \frac{h^{2}}{8\pi ^{2}I} \right )$$
  • $$n^{2}\left ( \frac{h^{2}}{8\pi ^{2}I} \right )$$
A $$U^{236}$$ sample of mass 1.0 g emits alpha particles at the rate $$1.24 \times 10^{4}$$ particles per second. (NA = $$6.023 \times 10^{23}$$)
  • The half life of this nuclide is $$4.5 \times 10^{9}$$ years
  • The half life of this nuclide is $$9 \times 1 0^{9}$$ years
  • The activity of the prepared sample is $$2.48 \times 10^{4}$$ particles/sec
  • The activity of the prepared sample is $$1.24 \times 10^{4}$$ particles/sec.
The orbital angular moments of an electron is $$\sqrt 3 \cfrac h {\pi}$$.Which of the following may be the permissible value of angular momentum of this electron revolving in an unknown orbit.
  • $$\cfrac h {\pi}$$
  • $$\cfrac h {2\pi}$$
  • $$\cfrac {3h} {2\pi}$$
  • $$\cfrac {2h} {\pi}$$
In a hydrogen atom the force acting on the electron is proportional to :
  • $$n^{4}$$
  • $$n^{-4}$$
  • $$r^{2}$$
  • $$n^{-2}$$
$$2N$$ molecules of an ideal gas '$$X$$' each of mass '$$m$$' and $$4N$$ molecules of another ideal gas $$Y,$$ each of mass $$3m$$ are maintained at the same absolute temperature in the same vessel. The rms velocity are $$V1$$ and $$V2$$ respectively then (along x-coordinate axis)$$\dfrac{v_x}{v_y}$$
  • $$\sqrt { 3 } : 1$$
  • $$1 : \sqrt { 3 }$$
  • $$3 : 1$$
  • $$1 : 3$$
An electron tube was sealed off during manufacture at a pressure of $$1.2 \times 10^{-7}$$ mm of mercury at $$27^oC$$. Its volume is $$100 cm^3$$. The number of molecules that remain in the tube is
  • $$2 \times 10^{16}$$
  • $$3 \times 10^{15}$$
  • $$3.86 \times 10^{11}$$
  • $$5 \times 10^{11}$$
The ratio of the orbit of the $$1st $$ three radii in an atom of hydrogen is 
  • $$1:2:3$$
  • $$3:2:1$$
  • $$1:4:9$$
  • $$9:4:1$$
Ratio of series limit of Brackett and Pfund series of hydrogen ato spectrum is
  • $$\dfrac{1}{4}$$
  • $$\dfrac{4}{9}$$
  • $$\dfrac{9}{16}$$
  • $$\dfrac{16}{25}$$
Orbital acceleration of electron in first orbit of hydrogen atom is:
  • $$\cfrac{h}{2\pi^2m^2r^3}$$
  • $$\cfrac{h^2}{2\pi^2m^2r^3}$$
  • $$\cfrac{h^2}{4\pi^2m^2r^3}$$
  • $$\cfrac{h^2}{4\pi^2m^2r^2}$$
Equivalent electric current created by electron of a H-atom in its ground using Bohr's model is nearly
  • $$2.14\times {10}^{-35}A$$
  • $$4.48\times {10}^{-30}A$$
  • $$24\times {10}^{-30}A$$
  • $$70\times {10}^{-35}A$$
Find the frequency of revolution of the electron in the first stationary orbit of H-atom 
  • $$8\times 10^{14}Hz$$
  • $$8.6\times 10^{10}Hz$$
  • $$8.6\times 10^{-10}Hz$$
  • $$8.12\times 10^{16}Hz$$
In hydrogen atom, the electron is making $$6.6\times 10^{15}rev/s$$ around the nucleus in an orbit of radius $$0.528A^0$$. The equivalent magnetic dipole moment is :
  • $$1\times 10^{-15}Am^2$$
  • $$1\times 10^{-10}Am^2$$
  • $$1\times 10^{-23}Am^2$$
  • $$1\times 10^{-27}Am^2$$
Alpha particles are projected towards fixed at a nucleus. Which of the paths shown in figure, is not possible
1243385_4ff6c8ffba024bb7ba8daa6421adf432.png
  • 1
  • 2
  • 3
  • 4
The Bohr radius of the fifth electron of phosphorus (atomic number = 15) acting as dopant in silicon (relative dielectric constant = 12) is 
  • 10.6$$\ { A^0 }$$
  • 0.53$$\ {   { A ^0} }$$
  • 21.2$$ { A^0 }$$
  • None of these
The radius of the orbit of an electron in a Hydrogen-like atom is $$3{ a }_{ 0 }$$, where $${ a }_{ 0 }$$ is the Bohr radius. Its orbital angular momentum is $$\frac { 3h }{ 2\pi  } $$. It is given that h is Planck's constant and R is Rydberg constant. The possible wavelength, when the atom de-excites is :
  • $$\dfrac { 4 }{ 5R } $$
  • $$\dfrac { 4 }{ 9R } $$
  • $$\dfrac { 1 }{ 2R } $$
  • $$\dfrac { 9 }{ 32R } $$
What is the ratio of the shortest wavelength of the Balmer series to the shortest wavelength of the Lyman series ?
  • 4 : 1
  • 4 : 9
  • 4 : 3
  • 5 : 9
The number of bond pair of electrons and lone pair of electrons in $$O_2$$ molecules respectively are
  • 2, 2
  • 2 ,1
  • 4, 2
  • 2, 4

In a cubical vessel $$1m \times 1m\times 1m$$ the gas molecules of diameter $$1.7 \times {10^{ - 8}}\;{\text{cm}}$$ are at a temperature 300 K and a pressure of $${10^{ - 4}}\;{\text{mm}}$$ mercury. The mean free path of the gas molecule is 
  • 1 meter
  • 4 meter
  • 2.42 meter
  • 1 cm
The figure indicates the energy level diagram of an atoms and the origin of six spectrum lines in emission (e.g line no.$$5$$ arises from the transition from level $$B$$ to $$A$$) Which of the following spectral lines will occur in the absorption spectrum?
1237701_64d3f59a81a540efb5c5d27c4609524a.png
  • $$4,5,6$$
  • $$1,2,3,4,5,6$$
  • $$1.2.3$$
  • $$1,4,6$$
Frequencies higher than $$10 MHz$$ are found not to be reflected by the particles present in the ionosphere then what is the maximum electron density of the ionosphere?
  • $$\dfrac{{{{10}^{14}}}}{81}e{m^{-3}}$$
  • $${10^{14}}e{m^{ - 3}}$$
  • $${10^{4}}e{m^{ - 3}}$$
  • $$\dfrac{{{{10}^{14}}}}{7}e{m^{ - 3}}$$
What will be relation between first bohr radius of H- atom and D-atom
  • $$r _ { H } = r _ { D }$$
  • $$r _ { H } > r _ { D }$$
  • $$r _ { \mathrm { H } } < \mathrm { r } _ { \mathrm { D } }$$
  • Can't predict
Which of the following is quantised according to Bohr's theory of hydrogen atom 
  • Linear momentum of electron
  • Angular momentum of electron
  • Linear velocity of electron
  • Angular velocity of electron
In a beryllium atom, if $$a_{0}$$ be the radius of the first orbit, then the radius of the second will be in general.
  • $$na_{0}$$
  • $$a_{0}$$
  • $$n^{2}a_{0}$$
  • $$\dfrac {a_{0}}{n^{2}}$$
The colour which corresponds to $$\mathrm { H } _ { \mathrm { B } } ( 4 \rightarrow 2 )$$ linein the Balmer series of hydrogen spectra is:
  • Green
  • Red
  • Violet
  • Blue
On a particular day,  the maximum frequency reflected from the ionosphere is 10 MHz. On another day, it was found to increase to 11 MHz. Calculate the ratio of maximum electron density of the ionosphere on the two days. 
  • $$1.21$$
  • $$0.82$$
  • $$0.50$$
  • $$0.25$$
When hydrogen atom is in its first excited level, its radius is _______ of the Bohr radius.
  • Twice
  • $$4$$ times
  • Same
  • Half
In a hydrogen like atom, when an electron jumps from the M-shell to the L-shell, the wavelength of emitted radiation is $$\lambda$$. If an electron jumps from N-shell to the L-shell, the wavelength of emitted radiation will be?
  • $$\dfrac{27}{20}\lambda$$
  • $$\dfrac{16}{25}\lambda$$
  • $$\dfrac{20}{27}\lambda$$
  • $$\dfrac{25}{16}\lambda$$
A proton and an $$\alpha$$ particle having equal kinetic energy are projected in a uniform transverse electric field as shown in figure


1331410_ed770d25f4cb4b00ba1707a5deffe1b0.png
  • Proton trajectory is more curved
  • $$\alpha$$ particle trajectory is more curve
  • Both trajectories are equally curved but in opposite direction
  • Both trajectories are equally curved and in same direction
Imagine an atom made up of proton and a a hypothetical particle of double the mass of the electron but having the same charge as the electron. Apply the Bohr atom model and consider all possible transitions of this hypothetical particle to the first excited level. The longest wavelength photon that will be emitted has wavelength $$\lambda $$ (give in term of the Rydberg constant R for the hydrogen atom) equal to
  • 9/5 R
  • 36/5 R
  • 18/5 R
  • 4/ R
In Bohr series of lines of hydrogen spectrum, third line from the red end corresponds to which one of the following inner orbit jumps of electron for Bohr's orbit in atom of hydrogen 
  • $$4\rightarrow 1$$
  • $$2\rightarrow 5$$
  • $$3\rightarrow 2$$
  • $$5\rightarrow 2$$
The distance between $$3^{rd}$$ & $$2^{nd}$$ Bohr orbit $$He^{+}$$ is 
  • $$2.645\ A^o$$
  • $$1.322\ A^o$$
  • $$0.2645\ A^{o}$$
  • $$None\ of\ these$$
The ratio of the radii of the first three Bohr orbit in H atom is 
  • $$1:\dfrac { 1 }{ 2 } :\dfrac { 1 }{ 3 } $$
  • $$1:2:3$$
  • $$1:4:9$$
  • $$1:8:27$$
the ground state energy of hydrogen  atom is -13.6 eV . the energy  of second excited state of $$He^{ + }$$ ion in eV is : 
  • $$-27.2$$
  • $$-3.4$$
  • $$-54.4$$
  • $$-6.04$$
The angular momentum of electron in 4th orbit of hydrogen atom is
  • $$\dfrac { 4h }{ \pi } $$
  • $$\dfrac { 2h }{ \pi } $$
  • $$\dfrac { nh }{ 2\pi } $$
  • $$\dfrac { h }{ 4\pi } $$
Imagine an atom made of a proton and a hypothetical particle of double the mass as that of an electron but the same charge. Apply Bohr theory to consider transitions of the hypothetical particle to the ground state . Then, the longest wavelength (in terms of Rydberge constant for hydrogen atom ) is
  • $$\dfrac { 1 } { 2 R }$$
  • $$\dfrac { 5} { 3 R }$$
  • $$\dfrac { 1 } { 3 R }$$
  • $$\dfrac { 2 } { 3 R }$$
According to Bohr's model, if the kinetic energy of an  electron in $$2^{nd}$$ orbit of $$He^{+}$$ is $$x$$, then what should be the ionisaion energy of the electron revolving in $$3^{rd}$$ orbit of $$m^{5+} ions>$$
  • $$X$$
  • $$4X$$
  • $$x/4$$
  • $$2X$$
Two electron separated by a distance $$r$$ experiences force $$F$$ between them . Then force between a proton and a singly ionized helium atom separated by a distance $$2r$$ is
  • $$4F$$
  • $$2F$$
  • $$\frac { F } {2}$$
  • $$\frac { F } {4 }$$
Hydrogen atom in ground state is excited by a monochromatic radiation of $$\lambda =975\mathring { A } $$ Number of spectral lines in the resulting spectrum emitted will be 
  • $$3$$
  • $$2$$
  • $$6$$
  • $$10$$
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