CBSE Questions for Class 12 Medical Physics Atoms Quiz 4 - MCQExams.com

Continuous spectrum is not due to
  • Hydrogen flame
  • Electric bulb
  • Kerosene oil lamp flame
  • Candle flame
Which of the following subshells is represented by the quantum numbers $$n$$=4 and $$l$$=1?
  • $$4s$$
  • $$4f$$
  • $$4d$$
  • $$4p$$
Match the following :
Type IType II
a) Continuous emission spectrume) Tungsten filament of bulb
b) Line emission spectrumf) $$CO_2$$ gas
c) Band emission spectrumg) Sodium vapour lamp
d) Line absorption spectrumh) chromosphere of sun
  • a-e; b-f; c-g; d-h
  • a-f; b-e; c-h; d-e
  • a-e; b-g; c-f; d-h
  • a-h; b-g; c-f; d-e
A cathode ray tube has a potential difference of $$V$$ between the cathode and anode. The speed of the cathode rays is given by
  • $$v \propto V$$
  • $$v \propto V^{-1}$$
  • $$v \propto \sqrt{V}$$
  • $$v \propto V ^{2}$$
Which of the following relates to photons both as wave motion and as a stream of particles?
  • Interference
  • $$E= mc^{2}$$
  • Diffraction
  • E $$= h\nu$$
When the particle and its anti-particle unite, the result is
  • A heavier particle
  • Two or more smaller particles
  • Photons
  • Partly matter and partly photons
In Rutherford's $$\alpha$$-rays scattering experiment, gold foils are used because of ___________.
  • high malleability
  • ductility
  • high melting point
  • high ionisation energy
Which of the following point is not shown by the Rutherford alpha scattering experiment?
  • $$\alpha$$ - particle can come within a distance of the order of $$10^{-14}  m$$ of the nucleus
  • The radius of the nucleus is less than $$10^{-14}  m$$
  • Sattering follows coulombs law
  • The positively charged parts of an atom move with extremely high velocities
Cathode rays are made to pass between the poles of a magnet as shown in figure. The effect of magnetic field is
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  • To deflect them towards the south pole
  • To deflect them perpendicular to the plane of the paper and towards the observer
  • To deflect them towards the north pole
  • To increase the velocity of the rays
The angular momentum of the $$\alpha -$$particles which are scattered through large angles by the heavier nuclei, is conserved because
  • of the nature of repulsive forces
  • the kinetic energy is conserved
  • the potential energy is conserved
  • there is no external torque
The force experienced by the cathode rays when they pass through a uniform electric field of intensity $$\bar{E}$$ is:
  • in the direction of the electric field
  • in the direction opposite to that of the electric field
  • at right angles to the electric field
  • zero, because cathode rays do not have any charge
In Rutherford's alpha-ray scattering experiment, a screen is used to detect the alpha particles which is coated by:
  • carbon black
  • platinum black
  • zinc sulphide
  • poly tetrafluoro ethylene
An electron makes transition from $$n= 3 , n=1$$ state in a hydrogen atom. The different possible number of photons that can be emitted is :
  • $$1$$
  • $$2$$
  • $$3$$
  • $$6$$
In the lowest energy level of hydrogen atom, electron has an angular momentum equal to:
  • $$\dfrac{\pi }{h}$$
  • $$\dfrac{h}{\pi }$$
  • $$\dfrac{h}{2\pi }$$
  • $$\dfrac{2\pi }{h}$$
The ionization energy of a hydrogen-like ion $$A$$ is greater than that of another hydrogen-like ion $$B$$. Let $$u$$ and $$E$$ represent the speed of the electron and energy of the atom respectively in the ground state. Then, 
  • $$r_{A}> r_{B}$$
  • $$u_{A}> u_{B}$$
  • $$E_{A}> E_{B}$$
  • $$L_{A}> L_{B}$$
In the Geiger-Marsden experiment, the force that scatters particles is 
  • nuclear force
  • coulomb force
  • both A and B
  • gravitational force
In Rutherford's 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 $$90^{0}$$ per minute by the same nucleus is:
  • $$28$$ per minute
  • $$112$$ per minute
  • $$12.5$$ per minute
  • $$7$$ per minute
The radius of hydrogen atom, when it is in its second excited state ,becomes $$\underline{\hspace{0.5in}}$$ its ground state radius. 
  • half
  • double
  • four times
  • nine times
The main defect of Bohr's atom model is :
  • mixing of classical and quantum theories
  • exclusion of nuclear motion
  • failed to explain the fine structure of spectral lines
  • failed to explain larger atoms
The electron is present in an orbit of energy state $$-1.51$$ eV, then angular momentum of the electron is
  • $$2h/\pi $$
  • $$h/\pi $$
  • $$3h/2\pi $$
  • $$7h/\pi $$
The possible values of principal quantum number can be:
  • $$1, 2, 3...8$$
  • $$0, 1, 2...8$$
  • only zero
  • only odd numbers
Atomic hydrogen is excited to the nth energy level.The maximum number of spectral lines which  it can emit while returing to the ground state, is
  • $$\frac{1}{2}n(n-1)$$
  • $$\frac{1}{2}n(n+1)$$
  • $$n(n+1)$$
  • $$n(n-1)$$
If $$A_{n}$$ is the area enclosed in the nth orbit in a hydrogen atom then the graph log $$\left ( \dfrac{A_{n}}{A_{1}} \right )$$ against log $$n$$
  • will have slope $$2$$ (straightline)
  • will have slope $$4$$ (straightline)
  • will be a monotonically increasing non linear curve
  • will be a circle
If an electron is revolving round the hydrogen nucleus at a distance of $$0.1\ nm$$, the speed should be :
  • $$2.188\times 10^{6}m/s$$
  • $$1.094\times 10^{6}m/s$$
  • $$4.376\times 10^{6}m/s$$
  • $$1.59\times 10^{6}m/s$$
When an electron jumps from higher orbit to the second orbit in hydrogen, the radiation emitted out will be in $$(R=1.09\times 10^{7}m^{-1})$$
  • ultraviolet
  • visible region
  • infrared region
  • X-ray region
The maximum number of photons emitted by an H-atom, if atom is excited to states with principal quantum number four is
  • $$4$$
  • $$6$$
  • $$2$$
  • $$1$$
The velocity of a helium nucleus travelling in a curved path in a magnetic field is $$V$$. The velocity of a proton moving in the same curved path in the same magnetic field is :
  • $$V$$
  • $$4V$$
  • $$2V$$
  • $$V/2$$
There are only three hydrogen atoms in a discharge tube. The analysis of spectrum shows that in all the hydrogen atoms, electrons are de-exciting from the fourth orbit. What should be the maximum number of spectral lines?
  • $$6$$
  • $$1$$
  • $$4$$
  • $$5$$
Rydberg atoms are the hydrogen atoms in higher excited states such atoms are observed in space.The orbit number for such an atom with radius about $$0.01\ mm$$ should be :
  • $$1$$
  • $$435$$
  • $$13749$$
  • $$117$$
The radius of shortest orbit in one electron system is $$18$$ pm.It may be.
  • $$_{1}^{1}H$$
  • $$_{2}^{1}H$$
  • $$He^{+}$$
  • $$Li^{+}$$
The threshold wavelength for a surface having a threshold frequency of $$0.6\times 10^{15}$$ Hz in ($$\mathring A$$) is
  • $$100$$
  • $$2000$$
  • $$5000$$
  • $$400$$
In one revolution round the hydrogen nucleus, an electron makes five crests .The electron belongs to
  • $$1^{st}$$ orbit
  • $$4^{th}$$ orbit
  • $$5^{th}$$ orbit
  • $$6^{th}$$ orbit

The ratio of momenta of an electron and a $$\alpha$$ -particle which is accelerated from rest by a potential difference of $$100 V$$ is:
  • 1
  • $$\displaystyle \sqrt {\dfrac{{2{m_e}}}{{{m_\alpha }}}} $$
  • $$\displaystyle \sqrt {\dfrac{{{m_e}}}{{{m_\alpha }}}} $$
  • $$\displaystyle \sqrt {\dfrac{{{m_e}}}{{2{m_\alpha }}}} $$
The energy of a hydrogen atom in the ground state is 13.6 eV. The energy of He+ ion in the first excited state will be
  • -13.6 eV
  • -27.2 eV
  • -54.4 eV
  • -6.8 eV
According to Bohr's theory of hydrogen atom, for an electron in the $$n^{th}$$ allowed orbit, then 
  • linear momentum is proportional to $$(1/n)$$
  • radius is proportional to $$n$$
  • the kinetic energy is proportional to $$(1/n^2)$$
  • the angular momentum is proportional to $$n$$
When a hydrogen atom is in its first excited level, its radius is
  • four times its ground state radius
  • twice times its ground state radius
  • same times its ground state radius
  • half times its ground state radius.
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.
  • $$2$$
  • $$3$$
  • $$5$$
  • $$6$$
Gold is chosen by Rutherford for his $$\alpha$$-ray scattering experiment because:
  • gold has high malleability
  • gold has high ductility
  • gold has high density
  • gold is the least reactive element
Rutherford's alpha ($$\alpha$$) particle scattering experiment resulted in discovery of:
  • electron
  • proton
  • nucleus in the atom
  • atomic mass
The time taken by a photo-electron to come out after the photon strikes is approximately
  • $$10^{-6}$$ sec
  • $$10^{-4}$$ sec
  • $$10^{-10}$$ sec
  • $$10^{-16}$$ sec
Rutherford's model explains :
  • Atom is a planetary model.
  • Electrons never loose nor gain energy.
  • Electron revolves around the nucleus with high velocities to counterbalance the forces of electrostatic forces of attraction between protons and electrons.
  • Electrons do not move at all.
When a hydrogen atom emits a photon of energy $$12.1 eV$$, its orbital angular momentum changes by
  • $$ 1.05 \times 10^{-34}$$Js
  • $$ 2.11 \times 10^{-34}$$Js
  • $$ 3.16 \times 10^{-34}$$Js
  • $$ 4.22 \times 10^{-34}$$Js
The fine structure of hydrogen spectrum can be explained by
  • the presence of neutrons in the nucleus.
  • the finite size of nucleus.
  • the orbital angular momentum of electrons.
  • the spin angular momentum of electrons.
In the hydrogen atom in the ground state
  • the kinetic energy of the electron is less than the potential energy which is positive
  • the potential energy is less than the kinetic energy which is positive
  • the potential energy is negative and the kinetic energy numerically less than the numerical value of potential energy
  • the total energy is negative
Rutherford experiment of scattering of $$\alpha$$ particles showed for the first time that the atom has:
  • electrons
  • only protons
  • nucleus
  • None of the above
A small positively charged nucleus is present in the center. Which observations tells about this?
  • 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
Which of the following products in a hydrogen atom is independent of principal quantum number $$n$$ ?
  • $$ v_r $$
  • $$ v_n $$
  • $$ E_r^{2}$$
  • $$ E_n$$
When a photomultiplier tube was used , the photo current recorded is 60 $$\mu A$$. The actual photo current is
  • $$\displaystyle > 60$$ $$ \mu A$$
  • $$\displaystyle = 60$$ $$ \mu A$$
  • $$\displaystyle < 60$$ $$ \mu A$$
  • None of these
Cathode ray oscillograph is used for
  • Taking X-ray photographs
  • Showing pictures
  • Demonstrating electrical pulses
  • Producing elementary particles
Rutherford's scattering experiment is related to the size of the:
  • nucleus
  • atom
  • electron
  • neutron
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