Question

A object of height 5 cm placed at a distance of 10 cm from the concave lens
of focal length 15.5 cm. Find the magnification and also find the nature and
position of the image.

Answer 1

Answer:

Given,

Size of object  h  

o

​  

=5cm

Size of the image  h  

i

​  

=?

Focal length,  f=−10cm

Object distance  u=−60cm

Image distance  v=?

Using mirror formula,  

f

1

​  

=  

v

1

​  

+  

u

1

​  

 

−10

1

​  

=  

v

1

​  

+  

−60

1

​  

 

v

1

​  

=  

60

−6+1

​  

 

v=−12cm

Hence, the position of the object is at 12 cm in front of the mirror.

Magnification (M)=  

h  

o

​  

 

h  

i

​  

 

​  

=  

u

−v

​  

=  

−60

12

​  

=−0.2

h  

i

​  

=−0.2×h  

o

​  

 

h  

i

​  

=−0.2×5=−1cm

Height of inverted image is 1cm.

Explanation: