$A$ man standing in a swimming pool looks at a stone lying at the bottom. The depth of the swimming pool is $h$. At what distance from the surface of water is the image of the stone formed? (Line of vision is normal; Refractive index of water is $n$)

An ice cube has a bubble inside. When viewed from one side,the apparent distance of the bubble is $12 \ cm$. When viewed from the opposite side,the apparent distance of the bubble is observed as $4 \ cm$. If the side of the ice cube is $24 \ cm$,the refractive index of the ice cube is $.....$.

$A$ paraxial beam is incident on a glass $(n = 1.5)$ hemisphere of radius $R = 6\, cm$ in air as shown. The distance of the point of convergence $F$ from the plane surface of the hemisphere is......$cm$.

$A$ glass tumbler having an inner depth of $17.5 \, cm$ is kept on a table. $A$ student starts pouring water $(\mu = 4/3)$ into it while looking at the surface of water from above. When he feels that the tumbler is half-filled,he stops pouring water. Up to what height,the tumbler is actually filled? (In $cm$)

$A$ bird is flying $3\, m$ above the surface of water. If the bird is diving vertically down with speed $= 6\, m/s$,its apparent velocity as seen by a stationary fish underwater is $m/s$.

Some water is filled in a container of height $30 \, cm$. If it is to appear half-filled to the observer when viewed from the top of the container, the height up to which water should be filled in it is [Refractive index of water $= \frac{4}{3}$] (in $cm$)