If `hat(i)` denotes a unit vector along incident light ray, `hat (r)`a unit vector along refracted ray into a medium of refraction index `mu` and `hat (n)` unit vector normal to boundary of medium directed towards incident medium, then law of refraction is
A. `hat(i).hat(n)=mu(hat(r).hat(n))`
B. `hat(i)xxhat(n)=mu(hat(n)xxhat(r))`
C. `hat(i)xxhat(n)=mu(hat(r)xxhat(n))`
D. `mu(hat(i)xxhat(n))=hat(r)xxhat(n)`
