When the same monochromatic ray of light travels through a glass slab and through water,the number of waves in a glass slab of thickness $5 \ cm$ is the same as in a water column of height $6 \ cm$. If the refractive index of glass is $1.56$,then the refractive index of water is:

An air bubble in a glass slab of thickness $15 \, cm$ appears to be at $6 \, cm$ from one side and at $4 \, cm$ from the opposite side. The refractive index of the glass is:

$A$ plane mirror is placed at the bottom of a tank containing a liquid of refractive index ' $\mu$ '. ' $P$ ' is a small object at a height ' $h$ ' above the mirror. An observer ' $O$ ' vertically above ' $P$ ' outside the liquid sees ' $P$ ' and its image in the mirror. The apparent distance between these two will be

$A$ vessel of depth $d$ is half filled with oil of refractive index $n_1$ and the other half is filled with water of refractive index $n_2$. The apparent depth of this vessel when viewed from above will be

$A$ glass slab of thickness $4 \ cm$ contains the same number of waves as $5 \ cm$ of water when both are traversed by the same monochromatic ray of light. The refractive index of water is $4/3$. What is the refractive index of glass?

$A$ rectangular tank of depth $8 \, m$ is full of water $(\mu = 4/3)$. The bottom is seen at an apparent depth of: