An initially parallel cylindrical beam travels in a medium of refractive index $\mu(I) = \mu_0 + \mu_2I$,where $\mu_0$ and $\mu_2$ are positive constants and $I$ is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. As the beam enters the medium,it will:

• A
  travel as a cylindrical beam
• B
  diverge
• C
  converge
• D
  diverge near the axis and converge near the periphery