In a hypothetical Bohr hydrogen, the mass of the electron is doubled. The energy ${\mathrm{E}}_{0}$ and the radius ${\mathrm{r}}_{0}$ of the first orbit will be (${\mathrm{a}}_{0}$ is the Bohr radius)
(a)
(b)
(c)
(d)

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A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for exciting electron from first to third Bohr orbit in ${\mathrm{Li}}^{++}$ will be (Ionisation energy of hydrogen atom is 13.6eV)
(a) 182.51 Å                 (b) 177.17 Å
(c) 142.25 Å                 (d) 113.74 Å

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The ionisation potential of H-atom is  13.6 V. When it is excited from ground state by monochromatic radiations of , the number of emission lines will be (according to Bohr’s theory)
(a) 10            (b) 8
(c) 6              (d) 4

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A neutron with velocity V strikes a stationary deuterium atom. Its kinetic energy changes by a factor of
(a) $\frac{15}{16}$              (b) $\frac{1}{2}$
(c) $\frac{2}{1}$                (d) None of these

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Mass-energy equivalent
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The sun radiates energy in all directions. The average radiations received on the earth surface from the sun is 1.4 $\mathrm{kilowatt}/{\mathrm{m}}^{2}$.The average earth- sun distance is $1.5×{10}^{11}$ metres. The mass lost by the sun per day is
(1 day = 86400 seconds)
(a)           (b)
(c)          (d)

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Mass-energy equivalent
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The binding energy per nucleon of ${\mathrm{O}}^{16}$ is 7.97 MeV and that of ${\mathrm{O}}^{17}$ is 7.75 MeV. The energy (in MeV) required to remove a neutron from ${\mathrm{O}}^{17}$ is
(a) 3.52                 (b) 3.64
(c) 4.23                 (d) 7.86

Concept Questions :-

Nuclear binding energy
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The rest energy of an electron is 0.511 MeV. The electron is accelerated from rest to a velocity 0.5 c. The change in its energy will be
(a) 0.026 MeV            (b) 0.051 MeV
(c) 0.079 MeV            (d) 0.105 MeV

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Mass-energy equivalent
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For uranium nucleus how does its mass vary with volume

(a) $\mathrm{m}\propto \mathrm{V}$           (b) $\mathrm{m}\propto 1/\mathrm{V}$
(c)        (d) $\mathrm{m}\propto {\mathrm{V}}^{2}$

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The rest mass of an electron as well as that of positron is 0.51 MeV. When an electron and positron are annihilated, they produce gamma-rays of wavelength(s)-

(a) 0.012 Å               (b) 0.024 Å
(c) 0.012 Å to $\infty$      (d) 0.024 Å to $\infty$

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Mass-energy equivalent
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In the nuclear fusion reaction ${}_{1}{}^{2}\mathrm{H}+{}_{1}{}^{3}\mathrm{H}\to {}_{2}{}^{4}\mathrm{He}+\mathrm{n}$ given that the repulsive potential energy between the two nuclei is , the temperature at which the gases must be heated to initiate the reaction is nearly
[Boltzmann’s constant )
(a)            (b)
(c)            (d)

Concept Questions :-

Mass-energy equivalent