The refractive index of water is 4/3 and for glass is 3/2 w.r.t air. What is the refractive index of glass w.r.t. water?

refractive index of water with respect to air = 4/3

that means

speed of light in air/speed of light in water = 4/3 --------------- (1)

and

refractive index of glass with respect to air = 3/2

that means

speed of light in air/ speed of light in glass = 3/2 - - - - -- - -- - - - -- - -(2)

we want

speed of light in water / speed of light in glass

so by dividing eq 2 by eq 1

we getspeed of light in water / speed of light in glass = 9/8