Question

7. An object 5 cm high is placed at a distance of 20 cm from a convex mirror of radius of curvature 30 cm. Find the position ,nature and size of image. *

(a) 50/7cm, 14/7cm

(b) 55/7cm, 16/7cm

(c) 60/7cm, 15/7cm

(d) 65/7cm, 17/7cm

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Answer 1

Answer:

Explanation:

u = - 20 cm

ho = 5 cm

R = + 30 cm ... (convex mirror)  

begin mathsize 12px style straight f equals straight R over 2 equals 30 over 2 equals plus 15 space cm space left parenthesis convex space mirror right parenthesis

From space the space mirror space formula comma space we space get

1 over straight f equals 1 over straight u plus 1 over straight v

rightwards arrow 1 over straight v equals 1 over straight f minus 1 over straight u

rightwards double arrow 1 over straight v equals 1 over 15 minus fraction numerator 1 over denominator negative 20 end fraction

rightwards double arrow straight v equals 8.57 space cm end style

The image is formed at a distance of 8.57 cm behind the convex mirror. Thus, it is virtual and erect.

 

m space equals space minus space v over u space space

m space equals negative space space fraction numerator 8.75 over denominator negative space 20 end fraction space equals space 0.4 space

A l s o comma

m space equals space h subscript i over h subscript o space

0.4 space equals h subscript i over 5 space

h subscript i space end subscript space equals space 0.4 space cross times space 5 space equals space 2 space c m

 

Thus, the height of an image is 2 cm.  

Thus, we can say that tha image is diminished.