An object of size $50 \mathrm{cm}$, placed in front of a spherical mirror at$20 \mathrm{cm}$, forms an image of size $25 \mathrm{cm}$ above the principal axis. Find out the focal length with sign convention and the type of spherical mirror used?

A particle is oscillating on the $x$-axis with an amplitude $2 \mathrm{cm}$ about the point $x_0=10 \mathrm{cm}$ with a frequency. A concave mirror of focal length $5 \mathrm{cm}$ is placed at the origin (see figure).

Identify the correct statements?
(i) The image executes periodic motion.
(ii) The image executes non-periodic motion.
(iii) The turning points of the image are asymmetric with respect to the image of the point at $X=10 \mathrm{cm}$.
(iv) The distance between the turning points of the oscillation of the image is $\frac{100}{21}\mathrm{ }\mathrm{cm}$.

A point object is moving uniformly towards the pole of a concave mirror of focal length $25 \mathrm{cm}$ along its axis as shown below. The speed of the object is $1 {\mathrm{ms}}^{-1}$. At $t=0$, the distance of the object from the mirror is $50 \mathrm{cm}$. The average velocity of the image formed by the mirror between time $t=0$ and $t=0.25 \mathrm{s}$ is:

A spherical mirror is obtained as shown in the figure from a hollow glass sphere, if an object is positioned in front of the mirror, what will be the nature and magnification of the image of the object? (Figure down as schematic and not to scale)