Question

An object is placed at 3cm in front of concave mirror(f=12cm). Now mirror moves away from object by 1cm. Find distance moved by image​

Answer 1

object is placed at distance of 20 cm in front of concave mirror.  

u = - 20 cm ( object is placed to the left of the mirror)  

focal length of concave mirror, f= - 12 cm (focal length of concave mirror)  

To find: position of image, v

 

By mirror formula,  

 

1 over f equals 1 over v plus 1 over u

 

fraction numerator 1 over denominator negative 12 end fraction equals 1 over v plus fraction numerator 1 over denominator negative 20 end fraction

1 over v equals fraction numerator 1 over denominator negative 12 end fraction minus fraction numerator 1 over denominator negative 20 end fraction

1 over v equals negative space 8 over 240 equals negative space space 0.033

rightwards double arrow space v equals space space minus 30 space c m

space

The negative sign indicates that the image is formed at the same side as that of object. The image distance is 30 cm.

Thus, it is formed beyond centre of curvature and the nature of image is real, inverted and magnified.