The diameter of the sun subtends an angle of $0.5°$ at the surface of the earth. A converging lens of focal length $100 \mathrm{cm}$ is used to provide an image of the sun onto a screen. The diameter (in mm) of the image formed is nearly

A thin symmetrical double convex lens of power $P$ is cut into three parts, as shown in the figure. Power of $A\mathit{ }$is:

In the figure given below, there are two convex lens $L_1$ and $L_2$ having focal length of $f_1$ and $f_2$ respectively. The distance between $L_1$ and $L_2$ will be

What should be the value of distance $d$ so that the final image is formed on the object itself. (focal lengths of the lenses are as given in the figure).