JEE MAIN - Physics (2010 - No. 8)
The speed of light in the medium is
minimum on the axis of the beam
the same everywhere in the beam
directly proportional to the intensity $$I$$
maximum on the axis of the beam
Обяснение
The speed of light $$(c)$$ in a medium of refractive index $$\left( \mu \right)$$ is given by
$$\mu = {{{c_0}} \over c},$$ where $${c_0}$$ is the speed of light in vacuum
$$\therefore$$ $$c = {{{c_0}} \over \mu } = {{{c_0}} \over {{\mu _0} + {\mu _2}\left( I \right)}}$$
As $$I$$ is decreasing with increasing radius, it is maximum
on the axis of the beam. Therefore, $$c$$ is minimum on the axis of the beam.
$$\mu = {{{c_0}} \over c},$$ where $${c_0}$$ is the speed of light in vacuum
$$\therefore$$ $$c = {{{c_0}} \over \mu } = {{{c_0}} \over {{\mu _0} + {\mu _2}\left( I \right)}}$$
As $$I$$ is decreasing with increasing radius, it is maximum
on the axis of the beam. Therefore, $$c$$ is minimum on the axis of the beam.