Question

6. (a) A linear object of size 4cm is placed in front of concave mirror of focal length 10cm
at a distance of 20cm in front of mirror. Find position, nature and size of image
*4marks)​

Answer 1

Answer:

Object distance u=−10 cm

Radius of curvature of concave mirror  R=−15 cm

Thus its focal length f=  

2

R

​  

=−  

2

15

​  

 cm

Using mirror formula :    

v

1

​  

+  

u

1

​  

=  

f

1

​  

 

∴  

v

1

​  

+  

−10

1

​  

=−  

15

2

​  

 

⟹ v=−30 cm

Magnification m=  

u

−v

​  

 

∴ m=  

−10

−(−30)

​  

=−3

Negative sign indicates that the image formed is inverted in nature.

Magnitude of magnification is greater than 1 which indicates that magnified image is formed.

Explanation: