Given below are four statements- (p) The second principal focus of a lens is the position of the object, real or virtual whose image is at infinity. (q) The second principal focus of a lens is the position of the image, real or virtual whose object is at infinity. (r) The first principal focus of a lens is the position of the object, real or virtual whose image is at infinity. (s) The first principal focus of a lens is the position of the image, real or virtual whose object is at infinity. Examine the above statements and find which among then are correct. Correct Answer (q) & (r) CONCEPT: Nature, position, and relative size of the image formed by a convex lens for various positions of the object:- Position of the object Position of the image The relative size of the image Nature of the image At infinity At focus F2 Highly diminished, point-sized Real and inverted Beyond 2F1 Between F2 and 2F2 Diminished Real and inverted At 2F1 At 2F2 Same size Real and inverted Between F1 and 2F1 Beyond 2F2 Enlarged Real and inverted At focus F1 At infinity Infinitely large or highly enlarged Real and inverted Between focus F1 and optical center O On the same side of the lens as the object Enlarged Virtual and erect EXPLANATION: From the above discussion we can say that, statement q and r are correct. So option 1 is correct.