Question

Q.24 A cyclotron is used to accelerate protons to a kinetic energy of 5 MeV. If the strength of magnetic

field in the cyclotron is 2T, find the radius and the frequency needed for the applied alternating

voltage of the cyclotron. (Given: Velocity of proton = 3  107

m/s) (3)

Q.25 Assuming expression for impedance in a parallel resonant circuit, state the conditions for parallel

resonance. Define resonant frequency and obtain an expression for it. (3)

Q.26 Using an expression for energy of electron, obtain the Bohr’s formula for hydrogen spectral lines.

OR

State the law of radioactive decay. Hence derive the relation N = N0e

t

. Represent it graphically. (3)

[15]



Q.27 Show that even as well as odd harmonics are present as overtones in the case of an air column

vibrating in a pipe open at both the ends. (3)

A wheel of moment of inertia 1 kg m2

is rotating at a speed of 30 rad/s. Due to friction on the axis,

it comes to rest in 10 minutes. Calculate the average torque of the friction. (2)

OR

Explain the formation of stationary waves by the analytical method. Show that nodes and antinodes

are equally spaced in stationary waves. (3)

The radius of gyration of a body about an axis, at a distance of 0.4 m from its centre of mass is

0.5 m. Find its radius of gyration about a parallel axis passing through its centre of mass. (2)

Q.28 Obtain an expression for potential energy of a particle performing S.H.M. What is the value of

potential energy at (i) Mean position and (ii) Extreme position. (3)

A stretched sonometer wire is in unison with a tuning fork. When the length of the wire is increased

by 5%, the number of beats heard per second is 10. Find the f
A sonometer wire 1 metre along weighing 2 g is in resonance with a tuning fork of frequency

300 Hz. Find tension in the sonometer wire. (2)

Q.29 Explain refraction of light on the basis of wave theory. Hence prove the laws of refraction. (3)

Two coherent sources of light having intensity 81:1 produce interference fringes. Calculate the ratio

of intensities at the maxima and minima in the interference pattern. (2)

OR

State Brewster’s law and show that when light is incident at polarizing angle, the reflected and

refracted rays are mutually perpendicular to each other. (3)

Monochromatic light of wavelength 4300 Å falls on a slit of width ‘a’. For what value of ‘a’ the

first maximum falls at 30°? (2)



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Answer 1

Answer:

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Explanation: