ExamsMy practice
Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :
- Statement I is false but Statement II is true
- Both Statement I and Statement II are false
- Both Statement I and Statement II are true
- Statement I is true but Statement II is false
Answer
(2) Both Statement I and Statement II are false
Solution
Statement I: For a concave lens f = -F and the centre of curvature is at 2F (with = 1.5). For a real object u = -2F:
1v = 1f + 1u = - 1F - 12F v = - 2F3
So the image is virtual, on the same side, between the lens and its focus, not at the centre of curvature on the other side. Statement I is false.
Statement II: For a virtual object (converging beam) lying between the lens and its focus, u = +x with x < F, so 1v = 1x - 1F > 0 and the image is real. Hence a concave lens does not always form a virtual image, so Statement II is false.
Answer: (2)
Note: The official NTA answer key gives option (1). Our faculty team has re-checked this question and finds option (2) correct, as explained above.