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
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
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
|Positions of Object and Image in Concave Mirror|
|Position of Object||Position of Image||Size of Image||Nature 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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