$A$ beam of light is converging towards a point $I$ on a screen. $A$ plane glass plate of thickness $t$ and refractive index $\mu$ is introduced in the path of the beam. The convergence point is shifted by:

• A
  $t \left( 1 - \frac{1}{\mu} \right)$ away
• B
  $t \left( 1 + \frac{1}{\mu} \right)$ away
• C
  $t \left( 1 - \frac{1}{\mu} \right)$ nearer
• D
  $t \left( 1 + \frac{1}{\mu} \right)$ nearer