// Additional solved numerical questions  , Example(set 1) 6 , pg 348
n1=1.5    //refractive index  of  core
n2= 1.47    // cladding refractive index
theta_c=asin(n2/n1)   //critical angle (in radian)
printf("critical angle=\n")
printf("theta_c=%.2f  degree",(theta_c*180)/%pi)