CBSE Questions for Class 12 Medical Physics Atoms Quiz 11 - MCQExams.com

The ratio of the frequencies of the long wavelength limits of the Lyman and Balmer series of hydrogen is:
  • $$27 : 5$$
  • $$5 : 27$$
  • $$4 : 1$$
  • $$1 : 4$$
The anode voltage of a photocell is kept fixed. The wavelength (i) of light falling on the cathode is gradually changed. The plate current (I) of the photocell varies as 
The shortest wavelength in the Lyman series of hydrogen spectrum is 912 A corresponding to a photon energy of 13.6 eV. The shortest wavelength in the Balmer series is:
  • $$3648 A^o$$
  • $$228 A^o$$
  • $$6566 A^o$$
  • $$8208 A^o$$
Rutherford's experiment on scattering of particles showed for the first time that the atom has:
  • electrons
  • protons
  • nucleus
  • neutrons
From lyman series of Pfund series, frequency__________
  • increase
  • decrease
  • increase or decrease
  • no change
In the Geiger - Marsden scattering experiment, find the distance of closest approach to the nucleus of a $$7.7Mev$$ $$\alpha$$ - particle before it comes momentaily to rest and reverses its direction. ($$'Z'$$ for gold nucleus $$= 79$$)
  • $$10fm$$
  • $$20fm$$
  • $$30fm$$
  • $$40fm$$
In hydrogen atom, an electron makes transition from $$n=3$$ to $$n=2$$ state in time interval of $$1.2\times{10}^{-8}s$$. Calculate the average torque (in Nm) acting on the electron during this transition.
  • $$1.055\times{10}^{-26}$$
  • $$4.40\times{10}^{-27}$$
  • $$1.7\times{10}^{-26}$$
  • $$8.79\times{10}^{-27}$$
Time taken for an electron to complete one revolution in the Bohr orbit of hydrogen atom is:
  • $$\dfrac { 4\pi ^{ 2 }mr^{ 2 } }{ nh } $$
  • $$\dfrac { nh }{ 4{ \pi }^{ 2 }mr } $$
  • $$\dfrac { nh }{ 4{ \pi }^{ 2 }mr^{ 2 } } $$
  • $$\dfrac { h }{ 2\pi mr } $$
In which of the following system will the radius of the $$2^{nd}$$ orbit be minimum? 
  • $$H$$
  • $$Mg^{+2}$$
  • $$He^+$$
  • $$B$$
According to Bohr hydrogen atom model the radius of stationary orbit directly proportional to principal quantum number n as $$\rightarrow $$
  • $$\dfrac { 1 }{2 n } $$
  • $$n^2$$
  • $${ n } $$
  • none of these
The energy of electron in the excited state of hydrogen atom is $$-0.85 eV$$. If 'h' is Plank's constant, the angular momentum of electron in the excited state is :
  • $$\dfrac{4h}{2 \pi}$$
  • $$h$$
  • $$\dfrac{3 h}{2 \pi}$$
  • $$\dfrac{h}{\pi}$$
The nuclear radius of a certain nucleus is  $$7.2 f m $$  and it has a charge of  $$1.28 \times 10 ^ { - 17 } { C }.$$  The number of neutrons inside the nucleus is
  • $$136$$
  • $$140$$
  • $$126$$
  • $$142$$
Two monochromatic light sources, $$A$$ and $$B$$, emit the same number of photons per second. The wavelength of $$A$$ is $${\lambda}_{A}=400nm$$ and that $$B$$ is $${\lambda}_{B}=600nm$$. The power radiated by source $$B$$ is
  • equal to that of source $$A$$
  • less than that of source $$A$$
  • greater than that of source $$A$$
  • cannot be compared to that from source $$A$$ using the available data.
The ratio of the kinetic energy to the total energy of an electron in a Bohr orbit is
  • $$1:-1$$
  • $$2$$
  • $$1 : 2$$
  • $$None$$
A certain dye absorbs light of $$\lambda =4000\overset { \circ  }{ A } $$ and emits fluorescent light of $$\lambda =5000\overset { \circ  }{ A } $$. Assuming that under given condition 50% of the absorbed energy is re-emitted out fluorescence, Calculate the ratio of the number of quanta emitted out to the number of quanta absorbed :   
  • $$\dfrac { 5 }{ 8 } $$
  • $$\dfrac { 8 }{ 5 } $$
  • $$\dfrac { 3 }{ 8 } $$
  • $$\dfrac { 8 }{ 3 } $$
According to Bohr's hypothesis , the angular momentum of the electron on any stationary orbit of radius r is proportional to ......
  • independent of r
  • 1/r
  • $$ \sqrt r $$
  • $$ r^2 $$

Find the average of radius for $$A{u^{197}}$$.
  • $$6.4\;{\text{fm}}$$
  • $$4.6\;{\text{fm}}$$
  • $$0.46\;{\text{fm}}$$
  • None of these
The size of an atom is of the order of
  • $$ 10^{-8} m $$
  • $$ 10^{-10} m $$
  • $$ 10^{-12} m $$
  • $$ 10^{-14} m $$
A photon and an electron both have wavelength 1A The ratio  of energy of photon to  that of electron is 
  • 1
  • 0.012
  • 82.7
  • $$10^{-10}$$
Wavelength of the first line of Balmer series is $$600nm$$. The wavelength of second line of the Balmer series will be:
  • $$444nm$$
  • $$800nm$$
  • $$388nm$$
  • $$632nm$$
In $$H$$-atm spectrum $$V$$ is the wave number
$$V_1 = V_{min} + V_{max}$$ for Lyman series
$$V_1 = V_{min} + V_{max}$$ for Balmer series then $$V_1 : V_2$$
  • $$9:2$$
  • $$3:2$$
  • $$5:2$$
  • $$7:2$$
An electron of H-atom de-excites from energy level $$n_1=2$$ to $$n_2=1$$ and the emitted photon is incident on $$He^+$$ ions in ground and first excited state. Which of following transition is possible.
  • $$n=1$$ to $$n=4$$
  • $$n=2$$ to $$n=4$$
  • $$n=2$$ to $$n=3$$
  • $$n=1$$ to $$n=3$$
The energy level diagram for an hydrogen like atom is shown in the figure.The radius of its first Bohr orbit is 
0 eV ____________n = $$\infty  $$
  -6.04 eV __________ n = 3 
 -13.6 eV ____________ n =2 
 -54.4 eV ____________ n=1
  • $$ 0.265 \mathring { A } $$
  • $$ 0.53 \mathring { A } $$
  • $$ 0.132 \mathring { A } $$
  • None of these
If $$ '\lambda ' $$ the longest wavelength of Lyman series, then shortest wavelength line that of the Balmer series is:-
  • $$ 5 \lambda $$
  • $$ 2 \lambda $$
  • $$ 4 \lambda $$
  • $$ 3 \lambda $$
The number density of molecules of a gas depends on their distance $$r$$ from the origin as, $$n(r) = n_0 e^{-\alpha r^4}$$. Then the total number of molecules is proportional to:
  • $$n_0 \alpha^{1/4}$$
  • $$n_0 \alpha^{-3}$$
  • $$n_0 \alpha^{-3/4}$$
  • $$\sqrt{n_0}\alpha^{1/2}$$
According to Bohr's theory, the product of velocity of electron in $$ n^{th} $$ orbit and the radius of $$ n^{th} $$ orbit is:
  • inversely proportional to the mass of the electron
  • directly proportional to the mass of the electron
  • independent of the mass of the electron
  • directly proportional to the square of mass of the electron
Taking the wavelength of first Balmer line in hydrogen spectrum ($$n=3$$ to $$n=2$$) as $$660nm$$, the wavelength of the 2nd Balmer line ($$n=4$$ to $$n=2$$) will be:
  • $$889.2nm$$
  • $$642.7nm$$
  • $$488.9nm$$
  • $$388.9nm$$
The ratio of mass densities of nuclei of $$^{40} Ca$$ and $$^{16} O$$ is close to :
  • $$1$$
  • $$2$$
  • $$0.1$$
  • $$5$$
In $$Li^{++}$$, electron in first Bohr orbit is excited to a level by a radiation of wavelength $$\lambda$$. when the ion gets deexcited to the ground state in all possible ways (including intermediate emissions), a total of six spectral lines are observed. What is the value of $$\lambda$$ ?
(Given : $$h = 6.63 \times 10^{34} Js$$;  $$ \, c = 3 \times 10^8 ms^{-1}$$)
  • $$9.4 nm$$
  • $$12.3 nm$$
  • $$10.8 nm$$
  • $$11.4 nm$$
In a muonic atom, a muon of mass of 200 times of that of electron and same charge is bond to the proton. The wavelengths of its Balmer series are in the range of  :
  • X-rays
  • infrared
  • $$\gamma$$ rays
  • microwaves
The total energy of an electron revolving in the second orbit of hydrogen atom is?
  • $$-13.6$$ eV
  • $$-1.51$$ eV
  • $$-3.4$$ eV
  • Zero
Which of the following is not a correct statement according to Rutherford's atomic model?
  • $$99\%$$ of mass of an atom is centered in the nucleus.
  • Most of the part inside the atom is empty.
  • The size of nucleus is very small in comparison to the atom.
  • Electrons revolve around the nucleus in a fixed circular path.
An experiment in which $$\alpha$$- particles were deflected by a gold foil produced new insights into the structure of the atom
Which conclusion can be drawn from the results of the experiment?
  • Atomic nuclei occupy a very small fraction of the volume of an atom
  • Electrons orbit the atomic nucleus
  • Some atoms of the same element contain different numbers of neutrons
  • The atomic nucleus contains protons and neutrons
A student measures the level of radiation emitted by a radioactive sample.
The table shows the readings she records on the counter over a short period of time.
Counter reading/ counts per minute$$106$$$$96$$$$98$$$$100$$
The sample is removed and the counter then shows a background radiation reading of $$4$$ counts per minute.
What is the best estimate for the average count rate due to the radioactive sample?
1643474_3ba21fda18d745b493862ec0be6a1e7b.png
  • $$96$$ counts per minute
  • $$98$$ counts per minute
  • $$100$$ counts per minute
  • $$104$$ counts per minute
The period of revolution of an electron in the ground state of hydrogen atom is T. The period of revolution of the electron in the first excited state is?
  • $$2$$ T
  • $$4$$ T
  • $$6$$ T
  • $$8$$ T
An excited $$He^+$$ ion emits two photons in succession, with wavelengths $$108.5 nm$$ and $$30.4 nm$$, in making a transition to ground state. The quantum number $$n$$, corresponding to its initial excited state is (for photon of wavelength $$\lambda$$, energy $$E = \dfrac{1240 eV}{\lambda (in\, nm)}$$)
  • $$n = 5$$
  • $$n = 4$$
  • $$n = 6$$
  • $$n = 7$$
The diagram shows a cathode-ray oscilloscope display of an electromagnetic wave. The time base setting is $$ 0.20 \mu s cm^{-1}$$. Which statement is correct? 

1648541_5c2b148539a34bee9def4919ee01c9fb.png
  • The frequency of the wave is 2.5 MHz and it lies in the microwave region of the
    electromagnetic spectrum
  • The frequency of the wave is 2.5 MHz and it lies in the radio-wave region of the
    electromagnetic spectrum.
  • The frequency of the wave is 5.0 MHz and it lies in the microwave region of the
    electromagnetic spectrum.
  • The frequency of the wave is 5.0 MHz and it lies in the radio-wave region of the
    electromagnetic spectrum.
The number of nodal sphere of $$3s-$$orbital are
  • $$1$$
  • $$2$$
  • $$3$$
  • $$0$$
Cathode rays are made to pass between the plates of a charged capacitor, It attracts.
  • Towards positive plate
  • Towards negative plate
  • (a) and (b) are correct
  • (a) and (b) are wrong
A moving electron has numerical relation $$\lambda = h$$. Then
  • $$m_{e} = \dfrac {1}{v_{e}}$$
  • $$v_{e} = \dfrac {1}{m_{e}}$$
  • Both (a) and (b)
  • None of these
The cathode ray particles originates in a discharge tube from the
  • Cathode
  • Anode
  • Source of high voltage
  • Residual gas
In Rutherford experiment the number of $$\alpha -$$particles scattered through an angle $$60^o$$ is $$112$$ per minute, then the number of $$\alpha -$$particles scattered through an angle of $$90^o$$ per minute by the same nucleus is :
  • $$28$$ per min
  • $$112$$ per min
  • $$12.5$$ per min
  • $$7$$ per min
Which of the following is incorrect regarding Rutherford's atomic model ?
  • Atom contains nucleus
  • Size of nucleus is very small in comparison to that of atom
  • Nucleus contains about $$90\%$$ mass of the atoms
  • Electrons revolve round the nucleus with uniform speed
For which of the following set of quantum numbers, an electron will have the lowest energy ?
  • $$3,2,1,\dfrac {1}{2}$$
  • $$4,2,-1,\dfrac {1}{2}$$
  • $$4,1,0,-\dfrac {1}{2}$$
  • $$5,0,0,\dfrac {1}{2}$$
Which is the common node for all orbitals:
  • $$x, y$$ and $$z-$$axis
  • $$xy, yz$$ and $$xz$$ planes
  • nodal spheres between two orbitals
  • nucleus
The angular momentum of the $$\alpha-$$particles which are scattered through large by the heavier nuclei, is conserved because of the  
  • nature of repulsive force
  • conservation of kinetic energy
  • conservation of potential energy
  • There is no external torque.
Which of the following curves may represent radius of orbit in $$H-$$atom as a function quantum number ?
The number of orbitals in $$3^{rd}$$ orbit are :
  • $$3$$
  • $$10$$
  • $$18$$
  • $$none\ of\ these$$
The order of size of nucleus and Bohr radius of an atom respectively are :
  • $$10^{-14}m, 10^{-10}m$$
  • $$10^{-10}m, 10^{-8}m$$
  • $$10^{-20}m, 10^{-16}m$$
  • $$10^{-8}m, 10^{-6}m$$
The radius of hydrogen atom, when it is in its second excited state, becomes :
  • half
  • double
  • four times
  • nine times
0:0:1


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