Formation of image depends upon the position of the object. There are six possibilities of the position of object in the case of concave mirror.
Since parallel rays coming from the object converge at principal focus, F of a concave mirror; after reflection. Hence, when the object is at infinity the image will form at F. Fig: Object at Infinity When object is placed between infinity and centre of curvature of a concave mirror the image is formed between centre of curvature (C) and focus (F). Fig: Object Between Infinity and C
Object between infinity and Centre of Curvature:
When the object is placed at centre of curvature (C) of a concave mirror, a real and inverted image is formed at the same position. Fig: Object at C When the object is placed between centre of curvature and principal focus of concave mirror, a real image is formed beyond the centre of curvature (C). Fig: Object between C and F
Object between Centre of curvature (C) and Principal Focus (F):
When the object is placed at principal focus (F) of a concave mirror, a highly enlarged image is formed at infinity. Fig: Object at F When the object is placed between principal focus and pole of a concave mirror, an enlarged, virtual and erect image is formed behind the mirror. Fig: Object between F and P
Object between Principal Focus (F) and Pole (P):
Positions of Object and Image in Concave Mirror Position of ObjectPosition of ImageSize of ImageNature of Image At infinity At focus Point sized, highly diminished Real and inverted Between infinity and C Between F and C Dminished Real and inverted At C At C Same size Real and inverted Between C and F Beyond C Enlarged Real and inverted At F At infinity Highly enlarged Real and inverted Between F and P Behind mirror Enlarged Virtual and erect
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With the help of a ray diagram, determine the position, nature and size of the image formed of an object placed at the centre of curvature of a concave mirror.
When an object is placed at the centre of curvature of a concave mirror, the image formed will be as shown:
The image of an object placed at the centre of curvature of a concave mirror is real, inverted and of the same size as the object.
Is there an error in this question or solution?
Page 2
Described with the help of a diagram, the nature, size and position of the image formed when an object is placed beyond the centre of curvature of a concave mirror.
The image formed by an object placed beyond the centre of curvature of a concave mirror is as follows:
The above shows that the image formed by the concave mirror is
- between the focus and centre of curvature
- real and inverted
- smaller than the object (or diminished)
Is there an error in this question or solution?
Option 4 : At the centre of curvature
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100 Questions 80 Marks 90 Mins
CONCEPT:
Different positions of the object and their image by a concave mirror:
Position of the object (Concave mirror) | Position of image | size of the image in comparison to the object | Nature of image |
At Infinity | At focus | Highly diminished | Real, inverted |
Between Infinity and the centre of curvature | Between the focus and centre of curvature | Diminished | Real, inverted |
At the centre of curvature | At the centre of curvature | Of the same size | Real, inverted |
At focus | At Infinity | Highly enlarged | Real, inverted |
Between the focus and centre of curvature | Between the centre of curvature and infinity | Enlarged | Real, inverted |
EXPLANATION:
- The position of the image formed by a concave mirror when the object is placed at the centre of the curvature of that spherical mirror is at the centre of curvature. So option 4 is correct.
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