. To construct a ray diagram we use two light rays which are so chosen that


(a) To construct a ray diagram we use two light rays which are so chosen that it is easy to know their directions after reflection from the mirror. List these two rays and state the path of these rays after reflection. Use these two rays to locate the image of an object placed between infinity and the centre of curvature of a concave mirror.

 

(b) Draw a ray diagram to show the formation of image of an object placed between the pole and principal focus of a concave mirror. How will the nature and size of the -image formed change, if the mirror is replaced by a converging lens of same focal length

Best Answer

(a) The rays for obtaining image from the mirror after reflection are so chosen that it is easy to know their directions after reflection from the mirror.

 

 (i) A ray parallel to the principal axis, after reflection passes through the focus in concave mirror  or  appears  to pass through the focus in convex Focus in mirror.

 

(ii) A ray passing through  the principal focus of a concave mirror or directed  towards the principal focus in convex mirror  after  reflection  will emerge   parallel   to the principal axis.

 

(iii) A ray passing through the centre  of curvature  of the-concave mirror or directed in the direction of the centre of curvature of the convex mirror is reflected back along the same path after reflection

 

To construct a ray diagram we use two light rays which are so chosen that

 

When the object is placed between infinity and the centre of curvature of a concave mirror

 

When the object is placed between infinity and the centre of curvature of

 

 

 

When the object is placed between the pole and principal focus of a concave mirror

 

When the object is placed between the pole and principal focus of

 

If the object is placed between the pole and principal focus of a converging lens (convex lens)

 

If the object is placed between the pole and principal focus of

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