$A$ boy stands straight in front of a mirror at a distance of $30 \ cm$ away from it. He sees his erect image whose height is $\frac{1}{5}$ of his real height. The mirror he is using is

If $x$ is the distance of an object from the focus of a concave mirror and $y$ is the distance of the image from the focus, then which of the following graphs is correct between $x$ and $y$?

In an experiment to determine the focal length $(f)$ of a concave mirror by the $u-v$ method,a student places the object pin $A$ on the principal axis at a distance $x$ from the pole $P$. The student looks at the pin and its inverted image from a distance keeping his/her eye in line with $PA$. When the student shifts his/her eye towards left,the image appears to the right of the object pin. Then,

Define the focal plane of a concave mirror.

$A$ short straight object of length $l$ lies along the central axis of a spherical concave mirror, at a distance $X$ from the mirror. The focal length of the mirror is $F$. If the length of the image in the mirror is $l^{\prime}$, then the ratio $\left(\frac{l^{\prime}}{l}\right)$ is (assume $l << X$ and $l << F$):

Define the following for curved mirrors: $(1)$ Radius of curvature,$(2)$ Centre of curvature,$(3)$ Pole,$(4)$ Principal axis,$(5)$ Aperture,$(6)$ Principal focus,$(7)$ Focal plane,$(8)$ Focal length,$(9)$ Paraxial rays.