Assertion: Geometrical optics can be regarded as the limiting case of wave optics.

Reason: When the size of the obstacle or opening is very large compared to the wavelength of light then wave nature can be ignored and light can be assumed to be traveling in a straight line.

In a medium the speed of light wave decreases to $0.2$ times to its speed in free space. The ratio of relative permittivity to the refractive index of the medium is $x:1$. The value of $x$ is ______.

(Given speed of light in free space $=3\times {10}^8 \mathrm{m} {\mathrm{s}}^{-1}$ and for the given medium ${\mu }_r=1$)

The radii of curvature of the faces of a double convex lens made of glass, are $10 \mathrm{cm}$ and $15 \mathrm{cm}$. Its focal length is $12 \mathrm{cm}$.

$\left(\mathrm{a}\right)$ Find the refractive index of glass

$\left(\mathrm{b}\right)$ Calculate its new focal length if the lens is completely immersed in water ( Refractive index of water is $\frac{4}{3}$)

How fast would a rocket have to go relative to an observer for its length to be corrected to $99\%$ of its length at rest? $\left(\mathrm{c}=3\times {10}^8{\mathrm{ms}}^{-1}\right)$

The following graph depicts the inverse of magnification versus the distance between the object and lens data for a setup. The focal length of the lens used in the setup is

Distance between the object and the lens $\left(\mathrm{m}\right)$

What determines the intensity of light in the photon picture of light?