Answer:
The correct option is;
(c) [tex]Speed \ of \ light \ in \ vacuum \times \dfrac{sin \, r}{sin \, i}[/tex]
Explanation:
The speed of light in a medium is calculated as follows;
[tex]Refractive \ index = \dfrac{sin \, i}{sin \, r} = \dfrac{Speed \ of \ light \ in \ vacuum}{Speed \ of \ light \ in \ medium}[/tex]
Therefore, we have;
[tex]Speed \ of \ light \ in \ medium = \dfrac{Speed \ of \ light \ in \ vacuum}{Refractive \ index } = \dfrac{Speed \ of \ light \ in \ vacuum}{ \dfrac{sin \, i}{sin \, r} }[/tex]
[tex]\dfrac{Speed \ of \ light \ in \ vacuum}{ \dfrac{sin \, i}{sin \, r} } = Speed \ of \ light \ in \ vacuum \times \dfrac{sin \, r}{sin \, i}[/tex]
[tex]\therefore Speed \ of \ light \ in \ medium = Speed \ of \ light \ in \ vacuum \times \dfrac{sin \, r}{sin \, i}[/tex]
