Q12 of 26 Page 1

Write three characteristic features in photoelectric effect which cannot be explained on the basis of wave theory of light, but can be explained only using Einstein’s equation.

1. When the radiation is directed on a said metal, the number of photoelectrons released per second is directly proportional to intensity of the radiation


2. To release photoelectrons the frequency required to cross the threshold frequency of the metal to release electrons freely.


3. Along with the frequency threshold the kinetic energy of the electron should also be considered as it is considered in Einstein’s equation as well.


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A charge is distributed uniformly over a ring of radius ‘a’. Obtain an expression for the electric intensity E at a point on the axis of the ring. Hence show that for points at large distances from the ring, it behaves like a point charge.

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(a) Write the expression for the magnetic force acting on a charged particle moving with velocity n in the presence of magnetic field B.

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(i) Define mutual inductance.

(ii) A pair of adjacent coils has a mutual inductance of 1.5 H. If the current in one coil changes from 0 to 20 A in 0.5 s, what is the change of flux linkage with the other coil?