. To construct a ray diagram we use two rays of light which are so chosen that it is easy to determine their directions after reflection from the mi


Choose  these two rays a d state the path of these rays after reflection from a concave mirror. Use these two rays to find the nature and position of the image of an object placed at a distance  of 15 cm from a concave mirror of focal length 10 cm.                                                                                 

Best Answer

Sol.   Ray 1. When an incident  ray of light is parallel to the principal axis of a concave mirror, its reflected ray must  pass through  the principal focus of the concave mirror.

Ray 2. A ray passing through. the principal focus of a concave mirror after reflection will emerge  parallel to the principal  axis.

•  Focal length = 10 cm; Then centre of curvature, C = 20 cm

• Object is placed at 15 cm, i.e., between  F & C

When the object is between F and C (centre of curvature):                                         

The image formed  is real, inverted  and  magnified. It is formed  beyond C.

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