The refractive indices of water and glass with respect to air are 4/3 and 3/2 respectively. If the speed of light in glass is 2x 10⁸ms _^-1, find the speed of light in

1. Air

2. Water

 Let the speed of light in air be x

Refractive index of glass = speed of light in air / speed of light in glass

 3 / 2= x / 2 * 10⁸ ms^-1

x =  3 * 2*  10⁸ ms^-1 / 2

x = 3 *  10⁸ ms^-1

 speed of light in air =  3 *  10⁸ ms^-1

2. Water

Refractive index of water = speed of light in air / speed of light in water

4 / 3 = 3 *  10⁸ ms^-1 / speed of light in water

speed of light in water =  3 *  10⁸ ms^-1 * 3 / 4 

speed of light in water =  9 *  10⁸ ms^-1 *  / 4 

speed of light in water = 2.2 * 10⁸ ms^-1  

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