In case of a concave mirror, if an object is placed between the principal focus F and pole P of the mirror, which one of the following statements about the image is NOT correct?
- (a)The image will be virtual
- (b)The image will be enlarged or magnified
- (c)The image will be formed at infinity
- (d)The image will be erect
Correct — C, the image will be formed at infinity. When an object lies between the pole P and the principal focus F of a concave mirror, the image formed is virtual, erect and enlarged, and it lies behind the mirror. So statements (a), (b) and (d) are all correct; the one that is NOT correct is (c) — the image is not formed at infinity. (An image at infinity forms only when the object is placed exactly at the focus F.)
- (a)The image will be virtual — This is a true statement, so it is not the answer: for an object between P and F the image is indeed virtual, formed behind the mirror.
- (b)The image will be enlarged or magnified — Also true — the virtual image formed is magnified, which is why a concave mirror is used as a shaving or make-up mirror; so it is not the incorrect statement.
- (d)The image will be erect — Also true — the virtual image is erect (upright), so this is not the incorrect statement either.
For a concave mirror the nature of the image depends on where the object is placed. With the object between the pole P and the focus F, the reflected rays diverge as if coming from behind the mirror, giving a virtual, erect and magnified image. This is the only object position for a concave mirror that produces a virtual image, and it is used in shaving and make-up mirrors.
The stem asks for the statement that is NOT correct. Three options describe the true image (virtual, magnified, erect); the odd one out is 'formed at infinity', which actually happens only when the object sits at the focus F.
- For a concave mirror with the object between the pole P and focus F, the image is virtual, erect and enlarged, and lies behind the mirror.
- An image at infinity forms only when the object is placed at the focus F.
- This 'between P and F' arrangement is used in shaving mirrors, make-up mirrors and dentists' mirrors.
- As the object moves from P towards F, the magnified virtual image grows larger.
Between P and F the image is virtual, erect and magnified; 'formed at infinity' (c) is the false statement.
- Confusing 'object at focus' (image at infinity) with 'object between P and F' (magnified virtual image).
- Reading the 'NOT correct' stem carelessly and picking a true statement.
Given an object position on a concave mirror, identify the nature of the image, or the statement that does NOT fit.
No directly related past PYQ was found.
- practice — not a real PYQ
A concave mirror forms a magnified, erect and virtual image when the object is placed
- (a)beyond C
- (b)at C
- (c)between P and F
- (d)at F
Answer(c) between the pole P and the focus F — as in a shaving mirror.
- practice — not a real PYQ
For a concave mirror, an image at infinity is formed when the object is placed
- (a)at the focus F
- (b)at the centre of curvature C
- (c)between F and C
- (d)beyond C
Answer(a) at the focus F.