$A$ beam of light is incident through the holes on side $A$ and emerges out of the holes on the other face of the box as shown in the Figure. Which of the following could be inside the box?

What is the relation between the radius of curvature $(R)$ and the focal length $(f)$ of a spherical mirror?

Draw a ray diagram showing the path of rays of light when it enters with oblique incidence: $(i)$ from air into water; $(ii)$ from water into air.

You have a spherical mirror. The image of an object placed in front of the mirror is virtual. If the position of the object is changed,the image remains virtual and erect. Is the spherical mirror concave or convex?

When an object is placed between the principal focus $(F)$ and the center of curvature $(C)$ of a concave mirror,what kind of image is formed?

$A$ $5 \, cm$ tall object is placed perpendicular to the principal axis of a convex lens of focal length $20 \, cm$. The distance of the object from the lens is $30 \, cm$. Find the $(i)$ position,$(ii)$ nature,and $(iii)$ size of the image formed.