Light starting from a medium of refractive index \[\mu \] undergoes refraction into a medium \[{{\mu }^{\text{l}}}\] If i and r stand for angles of incidence and refraction respectively, then

• A.  \[\frac{\sin i}{\sin r}=\frac{\mu }{{{\mu }^{\text{l}}}}\]                 
• B.  \[\frac{\sin i}{\sin r}=\frac{{{\mu }^{\text{l}}}}{\mu }\]
• C.  \[\frac{\cos i}{\cos r}=\frac{{{\mu }^{\text{l}}}}{\mu }\]                               
• D.  \[\frac{sini}{sinr}=\frac{1}{\mu {{\mu }^{\text{l}}}}\]