If an object of $4 \, cm$ height is placed at a distance of $12 \, cm$ from a concave mirror,then its image is formed at a distance of $24 \, cm$ from the mirror and behind it. What will be the height of the image (in $, cm$)?

The frequency,wavelength,or speed of light does not change on reflection.

Two adjacent walls and the ceiling of a rectangular room are mirror surfaced. The number of images of himself that an observer sees is

Where should the object be placed to obtain a real and diminished image using a concave mirror?

What is meant by power of a lens? Define its $SI$ unit. You have two lenses $A$ and $B$ of focal lengths $+10\, cm$ and $-10\, cm$ respectively. State the nature and power of each lens. Which of the two lenses will form a virtual and magnified image of an object placed $8\, cm$ from the lens? Draw a ray diagram to justify your answer.

With the help of a ray diagram,show the formation of an image by a convex lens when the object is placed between $F$ and $2F$. Write two characteristics of the image so formed.