Q19 of 36 Page 379

An object 2 cm in size is placed 30cm in front of a concave mirror of focal length 15cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? What will be the nature and the size of the image formed? Draw a ray diagram to show the formation of the image in this case.

According to the question;

Object distance (u) = -30cm;


Focal length (f) = -15cm;


Image distance = v;


By mirror formula;






⇒


⇒ v = 30cm.


Thus, screen should be placed 30cm in front of the mirror (Centre of curvature) to obtain the real image.


Height of object h1= 2cm;


Magnification = =


Putting values of v and u


Magnification =


⇒


⇒


Height of image is 2 cm.


Negative sign means image is inverted.


Thus real, inverted image of size same as that of object is formed.


Diagram below shows the image formation.



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