$A$ plane mirror is placed vertically facing due north. An arrow pointing north-east is kept in front of the mirror. In which direction will the arrow point in this image?

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

An object $3.0 \text{ cm}$ high is placed perpendicular to the principal axis of a concave lens of focal length $7.5 \text{ cm}$. The image is formed at a distance of $5.0 \text{ cm}$ from the lens. Calculate $(i)$ distance at which object is placed,and $(ii)$ size and nature of image formed.

An object is situated at $8 \, cm$ from a convex lens of focal length $10 \, cm$. Find the position and nature of the image. Draw a ray diagram to illustrate the formation of the image (not to scale).

If a convex lens forms a real and magnified image of an object,where is the object placed?

Write down four important characteristics of the image formed by a plane mirror.