For a colour of light,the wavelength in air is $6000 \ \mathring A$ and in water,the wavelength is $4500 \ \mathring A$. Then the speed of light in water will be:

When light enters glass from vacuum,then the wavelength of light

$A$ ray of light passes through four transparent media with refractive indices $\mu_1, \mu_2, \mu_3$ and $\mu_4$ as shown in the figure. The surfaces of all media are parallel. If the emergent ray $CD$ is parallel to the incident ray $AB$,we must have

An object is immersed in a fluid of refractive index $\mu$. In order that the object becomes invisible when observed from outside,it should

The refractive index of water and glass with respect to air is $1.3$ and $1.5$ respectively. Then the refractive index of glass with respect to water is

The absolute refractive indices of glass and water are $\frac{3}{2}$ and $\frac{4}{3}$,respectively. The ratio of the velocity of light in glass to that in water will be: