A plano convex lens of refractive index $$1.5$$ and radius of curvature $$30$$ $$cm$$. Is silvered at the curved surface. Now this lens has been used to form the image of an object. At what distance from this lens an object be placed in order to have a real image of size of the object

The image formed by an objective of a compound microscope is

To get three images of a single object, one should have two plane mirrors at an angle of

If two mirrors are kept at $${60^ \circ }$$ to each other, then the number of images formed by them is