The refractive index of water in a biology laboratory tank varies as $1.33 + 0.002 / \lambda^2$,where $\lambda$ is the wavelength of light. Small pieces of organic matter of different colours are seen at the bottom of the tank using a travelling microscope. Then,the image of the organic matter appears

$A$ ray of light travels from air to water to glass and again from glass to air. The refractive index of water with respect to air is '$X$', glass with respect to water is '$Y$', and air with respect to glass is '$Z$'. Which one of the following is correct?

The speed of light in a medium of refractive index $1.25$ is . . . . . . .
(Speed of light in vacuum is $3 \times 10^{8} \,m \,s^{-1}$)

If light passes near a massive object,the gravitational interaction causes a bending of the ray. This can be thought of as happening due to a change in the effective refractive index of the medium given by $n = 1 + \frac{2GM}{rc^2}$,where $r$ is the distance of the point of consideration from the centre of the mass of the massive body,$G$ is the universal gravitational constant,$M$ is the mass of the body,and $c$ is the speed of light in vacuum. Considering a spherical object,find the deviation of the ray from the original path as it grazes the object.

In refraction,light waves are bent on passing from one medium to a second medium because,in the second medium,

The refractive index of water is $1.33$. What will be the speed of light in water?