How is the image formed by concave mirror when object is at infinity

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

Properties of image:

• Point sized
• Highly diminished
• Real and inverted

Object between infinity and Centre of Curvature:

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

Properties of image:

• Diminished compared to object
• Real and inverted

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

Properties of image:

• Same size as object
• Real and inverted

Object between Centre of curvature (C) and Principal Focus (F):

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

Properties of image:

• Larger than object
• Real and inverted

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

Properties of image:

• Highly enlarged
• Real and inverted

Object between Principal Focus (F) and Pole (P):

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

Properties of image:

• Enlarged
• Virtual and erect