The magnification $m$ produced by a spherical mirror and a spherical lens is $+0.8$. Identify the nature of the mirror and the lens.

State where an object must be placed so that the image formed by a concave mirror is:
$(a)$ Erect and virtual.
$(b)$ At infinity.
$(c)$ The same size as the object.

The image formed by a spherical mirror is virtual. The mirror will be:

Study the given ray diagrams and select the correct statement from the following:
$(A)$ Device $X$ is a concave mirror and device $Y$ is a convex lens, whose focal lengths are $20 \text{ cm}$ and $25 \text{ cm}$ respectively.
$(B)$ Device $X$ is a convex lens and device $Y$ is a concave mirror, whose focal lengths are $10 \text{ cm}$ and $25 \text{ cm}$ respectively.
$(C)$ Device $X$ is a concave lens and device $Y$ is a convex mirror, whose focal lengths are $20 \text{ cm}$ and $25 \text{ cm}$ respectively.
$(D)$ Device $X$ is a convex lens and device $Y$ is a concave mirror, whose focal lengths are $20 \text{ cm}$ and $25 \text{ cm}$ respectively.

Which type of mirror can produce a virtual image?

$A$ concave mirror and a convex lens are held in water. What changes, if any, do you expect in their focal length?