An opaque card is held over the lower half of a converging lens as shown in the figure. Which picture best shows the image that appears on the screen?

$A$ good photographic print is obtained at a distance of $20 \,cm$ with an exposure time of $2 \,s$. What will be the exposure time required to get an equally good result at a distance of $40 \,cm$?

Ray optics is valid when characteristic dimensions are:

An object is placed $60 \ cm$ in front of a convex mirror of focal length $30 \ cm$. $A$ plane mirror is now placed facing the object in between the object and the convex mirror such that it covers the lower half of the convex mirror. What should be the distance of the plane mirror from the object so that there will be no parallax between the images formed by the two mirrors (in $cm$)?

What is an image? Explain its types.

$A$ prism having an apex angle $4^o$ and refractive index $1.5$ is located in front of a vertical plane mirror as shown in the figure. Through what total angle is the ray deviated after reflection from the mirror (in $^o$)?