Light travels through a glass plate of thickness $t$ and having refractive index $\mu$. If $c$ is the velocity of light in vacuum, the time taken by the light to travel through this thickness of glass is:

$A$ beam of light composed of red and green rays is incident obliquely at a point on the face of a rectangular glass slab. When coming out on the opposite parallel face, the red and green rays emerge from

An object lying $100 \ cm$ inside water is viewed normally from air. If the refractive index of water is $\frac{4}{3}$,then the apparent depth of the object is (in $cm$)

Obtain the relation between the real depth and apparent depth of the bottom of a tank filled with water when observed from air.

In determining the refractive index of a glass slab using a travelling microscope,the following readings are tabulated:
$(a)$ Reading of travelling microscope for ink mark $= 5.123 \ cm$
$(b)$ Reading of travelling microscope for ink mark through glass slab $= 6.123 \ cm$
$(c)$ Reading of travelling microscope for chalk dust on glass slab $= 8.123 \ cm$
From the data,the refractive index of a glass slab is:

If the velocity of light in vacuum is $3 \times 10^{8} \text{ m/s}$, the time taken (in nanoseconds) to travel through a glass plate of thickness $10 \text{ cm}$ and refractive index $1.5$ is: