$A$ 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

Consider a light source placed at a distance of $1.5 \ m$ along the axis facing the convex side of a spherical mirror of radius of curvature $1 \ m$. The position $(s^{\prime})$,nature and magnification $(m)$ of the image are

$A$ small candle,$2.5\; cm$ in size,is placed at $27\; cm$ in front of a concave mirror of radius of curvature $36\; cm$. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image. If the candle is moved closer to the mirror,how would the screen have to be moved?

$A$ concave mirror gives an image three times as large as the object placed at a distance of $20 \ cm$ from it. For the image to be real,the focal length should be ...... $cm$.

$A$ ray of light is incident on a concave mirror. It is parallel to the principal axis and its height from the principal axis is equal to the focal length of the mirror. The ratio of the distance of point $B$ (where the reflected ray intersects the principal axis) to the distance of the focus from the centre of curvature is ($AB$ is the reflected ray).

The focal length of a concave mirror is $20 \ cm$. Determine where an object must be placed to form an image,magnified two times and real.