# Concave Mirror

#### Topics

• Concave Mirror
• Application of Concave Mirror

## Notes

IMAGE FORMATION BY CONCAVE MIRROR:

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.

• Object at infinity
• Object between infinity and centre of curvature (C)
• Object at centre of curvature (C)
• Object between centre of curvature (C) and Principal focus (F)
• Object at Principal Focus (F)
• Object between Principal Focus (F) and Pole (P)

Object at infinity:

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.

• 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).

• Diminished compared to object
• Real and inverted

Object at Centre of Curvature (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.

• 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).

• Larger than object
• Real and inverted
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

## Notes

Uses of Concave Mirror:

• As reflector in electric torch, head lights of vehicle, search light, etc. The source of light is put at the focus of the reflector, which produces a strong parallel beam of light, which helps in clear visibility.
• As shaving mirror to produce larger image of face to facilitate better viewing during shaving.
• Concave mirror is used by dentists to see larger image of teeth of the patient. When a tooth is placed between focus and pole, the concave mirror produces a magnified image of the tooth.
• As reflector in solar furnace. By using concave mirror in solar furnace the concentrated rays of sunlight is obtained at focus which produces enormous amount of heat because of concentration.
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Light Reflection and Refraction part 6 (Image formation Concave Mirror) [00:13:10]
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