The correct option is B 1.25
We know that,
Refractive index of medium 2 with respect to medium 1, 1μ2=sped of light in medium 1speed of light in medium 2
We have to find the refractive index of glass with respect to water, so according to the above equation first we need to find the speed of light in water and glass.
Given, Speed of light in air =3×108m/s
So, Refractive index of water with respect to air,
airμwater=sped of light in airspeed of light in water
1.2 = 3 × 108speed of light in waterTherefore, speed of light in water=2.5×108 m/s
Similarly, Refractive index of glass with respect to air,airμglass=sped of light in airspeed of light in glass
1.5 = 3 × 108speed of light in glassTherefore, speed of light in glass=2×108 m/sHence, Refractive index of glass with respect to water is waterμglass=sped of light in waterspeed of light in glass = 2.5 × 1082 × 108 =1.25