A beam of light is converging towards a point `I` on a screen. A plane glass plate whose thickness in the direction of the beam `=t` , refractive index `=mu` , is introduced in the path of the beam. The convergence point is shifted by
A. `t(1-1/mu)` away
B. `t(1+1/mu)` away
C. `t(1-1/mu)` nearer
D. `t(1+1/mu)` nearer