Two statements are given $-$ one labelled Assertion $(A)$ and the other labelled Reason $(R).$ Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below:
Assertion $(A)$: We can decide the nature of a mirror by observing the size of the erect image formed in the mirror.
Reason $(R)$: The minimum distance between a real object and its real image in a concave mirror is zero.

When an object is placed $20 \text{ cm}$ from a concave mirror, a real image magnified three times is formed. Find:
$(a)$ The focal length of the mirror.
$(b)$ Where must the object be placed to give a virtual image three times the height of the object (in $\text{ cm}$)?

Two statements are given—one labeled Assertion $(A)$ and the other labeled Reason $(R)$. Select the correct answer to these questions from the codes $(a)$, $(b)$, $(c)$, and $(d)$ as given below:
$(a)$ Both $A$ and $R$ are true, and $R$ is the correct explanation of the assertion.
$(b)$ Both $A$ and $R$ are true, but $R$ is not the correct explanation of the assertion.
$(c)$ $A$ is true, but $R$ is false.
$(d)$ $A$ is false, but $R$ is true.
Assertion $(A)$: We can decide the nature of a mirror by observing the size of the erect image formed in the mirror.
Reason $(R)$: The minimum distance between a real object and its real image in a concave mirror is non-zero.

Draw the ray diagram in each case to show the position,nature,and size of the image formed when the object is placed:
$(i)$ At the centre of curvature of a concave mirror.
$(ii)$ Within the focal length of a convex lens.
$(iii)$ Between the pole and focus of a concave mirror.
$(iv)$ In front of a convex mirror.
$(v)$ In front of a concave lens.

For which type of mirror will the image always be erect,regardless of the distance at which the object is placed?

The image shows the path of light as it travels from one medium to another.
$9$. Based on the refraction observed, which pair of media could represent Medium $1$ and Medium $2$?

	Medium $1$	Medium $2$
$A$.	Water	Kerosene
$B$.	Kerosene	Diamond
$C$.	Flint glass	Water
$D$.	Kerosene	Flint glass

$10$. The power of a lens $(P)$ is calculated by the formula, $P = \frac{1}{f}$, where $f$ is the focal length of the lens in meters. A lens has a focal length of $-0.25 \ m$. Is it a convex lens or a concave lens? Explain your answer.