Question

light enters from air to glass plate having refractive index 1.50. what is speed of light in glass? the speed of light in vacuum is 3×10*8 m/s

Answer 1

$let \: speed \: of \: light \: in \: plate \: be \: v \\ refractive\: index \: of \: plate \: = \frac{speed \: of \: light \: in \: vacuum}{speed \: of \: light \: in \: plate} \\ 1.50 = \frac{3 \times {10}^{8} }{v} \\ v = \frac{3 \times {10}^{8} }{1.50} \\ v = 2 \times {10}^{8} {ms}^{ - 1} ..........answer$

Answer 2

According to the Question

Refractive index of glass = 1.5

Using Formula

Refractive index of a medium = $\bf\huge\frac{Speed\:of\:light\:in\:vaccum}{Speed\:of\:light\:in\:Medium}$

Hence  

Speed of light in glass = $\bf\huge\frac{Speed\:of\:light\:in\:vaccum}{Refractive\:Index\:of\:Glass}$

Speed of light in glass = $\bf\huge\frac{3\times 10^8}{1.5}$

Therefore

Speed of light in the glass is 2 * 10^8 m/s