The time taken by sunlight to cross a $5 \,mm$ thick glass plate $(\mu = 3/2)$ is

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

In the given diagram,the apparent velocity of a bird (coming toward a fish) as seen by the fish is $19 \, cm/s$. Find the actual velocity of the bird in $cm/s$.

Three immiscible transparent liquids with refractive indices $3/2, 4/3$ and $6/5$ are arranged one above the other in a container. The depths of the liquids are $3 \text{ cm}, 4 \text{ cm}$ and $6 \text{ cm}$ respectively. The apparent depth of the vessel is (in $\text{ cm}$)

Consider three media $P$, $Q$, and $R$ with refractive indices $1$, $1.25$, and $1.5$, respectively. The medium $Q$ having a thickness of $5 \text{ cm}$ is placed between extended media $P$ and $R$. An object $O$ is placed at the centre of medium $Q$. If viewed from medium $P$ near the normal direction, the apparent depth of $O$ is $h_1$. For similar observation from medium $R$, the apparent depth is $h_2$. The value of $|h_1 - h_2|$, in $\text{cm}$, is:

$A$ 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 $m/s$.