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.

Question

Question

This question was previously asked in

ALP CBT 2 Physics and Maths Previous Paper 2 (Held On: 21 Jan 2019 Shift 2)

Answer 1

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, statements q and r are correct. So option 1 is correct.