By which type of mirror,the image obtained is always erect?

$A$ convex mirror of focal length $15 \ cm$ and a concave mirror of focal length $10 \ cm$ are placed facing each other at a distance of $40 \ cm$ apart. $A$ point object is placed between the mirrors on their common axis at a distance of $15 \ cm$ from the concave mirror. The position of the image formed by reflection at the convex mirror will be at a distance of ..... $cm$ from it.

Assertion : $A$ red object appears dark in the yellow light.
Reason : The red colour is scattered less.

Which of the following form$(s)$ a virtual and erect image for all positions of the object?

Discuss the sign convention of distances for reflection by a spherical mirror and refraction by a spherical lens.

To find the focal length of a convex mirror,a student records the following data:

Object Pin	Convex Lens	Convex Mirror	Image Pin
$22.2 \, cm$	$32.2 \, cm$	$45.8 \, cm$	$71.2 \, cm$

The focal length of the convex lens is $f_1$ and that of the mirror is $f_2$. Taking index correction to be negligibly small,$f_1$ and $f_2$ are close to: