$A$ rod of length $10 \text{ cm}$ lies along the principal axis of a concave mirror of focal length $10 \text{ cm}$ as shown in the figure. The length of the image is . . . . . . $\text{cm}$.

$A$ straight line joining the object point and image point is always perpendicular to the mirror:

$A$ concave mirror of focal length $f$ (in air) is immersed in water $(\mu = 4/3)$. The focal length of the mirror in water will be

$A$ convex mirror of radius of curvature $30 \,cm$ forms an image that is half the size of the object. The object distance is: (in $\,cm$)

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

$A$ spherical mirror forms an erect image three times the linear size of the object. If the distance between the object and the image is $80 \, cm$,the focal length of the mirror is........ (in $, cm$)