Section – C
11. 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 distance from the ring, it
behaves like a point charge.
11. 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 distance from the ring, it
behaves like a point charge.
12. Write three characteristic features in photoelectric effect
which cannot be explained on the basis of wave throry of light, but
can be explained only using Einstein’s equation. [3]
Ans. (i) Existance of threshold frequency: According to wave
theory, there should not exist any threshold frequency but Einstein’s
theory explains the ejxistance of threshold frequency.
(ii) Dependence of kinetic energy on frequency of incident light: According
to wave theory, the maximum kinetic energy of emitted electrons should depend
on intensity of incident light and not on frequency where as Einstein’s equation e
xplains that it depends on frequency and not on intensity.
(iii) Instantaneous emission of electrons: According to wave theory there should
be time lag between emission of electrons and incident of light where as Einstein’s
equation explains why there is no time lag between incident of light and emission
of electrons.
which cannot be explained on the basis of wave throry of light, but
can be explained only using Einstein’s equation. [3]
Ans. (i) Existance of threshold frequency: According to wave
theory, there should not exist any threshold frequency but Einstein’s
theory explains the ejxistance of threshold frequency.
(ii) Dependence of kinetic energy on frequency of incident light: According
to wave theory, the maximum kinetic energy of emitted electrons should depend
on intensity of incident light and not on frequency where as Einstein’s equation e
xplains that it depends on frequency and not on intensity.
(iii) Instantaneous emission of electrons: According to wave theory there should
be time lag between emission of electrons and incident of light where as Einstein’s
equation explains why there is no time lag between incident of light and emission
of electrons.
