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Question 14 Marks
An electron in hydrogen atom revolving in a radius of $5.29 \times 10^{-11} m$ around the nucleus. According to the condition of Bohr's allowed electron orbits, find the principle quantum number corresponds to this orbit.
$\begin{array}{l}
h=6.625 \times 10^{-34} JS, e=1.6 \times 10^{-19} C \\
\varepsilon=8.85 \times 10^{-12} MKS, m=9.1 \times 10^{-31} kg
\end{array}$
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Question 34 Marks
Obtain the binding energy of the nuclei ${ }_{26}^{56} Fe$ and ${ }_{83}^{209} Bi$ in units of MeV from the following data :
$m\left({ }_{26}^{56} Fe\right)=55.934939 u, m\left({ }_{83}^{209} Bi\right)=208.980388 u$
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Question 44 Marks
A beam of light converges at a point $P$. Now a lens is placed in the path of the convergent beam 12 cm from P. At what point does the beam converge if the lens is (a) a convex lens of focal length 20 cm , and (b) a concave lens of focal length 16 cm ?
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Question 54 Marks
Obtain the relation of phase between instantaneous current and voltage with the help of phase diagram for series LCR circuit.
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Question 64 Marks
Resistance of tungsten filament in one bulb at $27{ }^{\circ} C$ is $18 \Omega$. When this bulb is connected to 60 V source, steady current passing through it is 0.3 A . Find temperature of this filament taking $\alpha=4.5 \times 10^{-3} K^{-1}$. Assume that Ohm's law is obeyed.
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