Question

A concave mirror with object placed at 10m distance with focal length 20m. Find the
position and nature of image​

Answer 1

Answer:

Given: f=15

           u=−10

From mirror formula,  

u

1

​  

+  

v

1

​  

=  

f

1

​  

 

                                   

−10

1

​  

+  

v

1

​  

=  

15

1

​  

 

                                  v=6 cm

Image is formed 6 cm to the right of the mirror. Image formed is virtual and erect.

Answer 2

Answer:

Given:

f = -20 cm

u = -10 cm  

By Mirror Formula, 1/v + 1/u = 1/f  

⇒1/v = 1/f - 1/u  

⇒1/v = 1/-20 - 1/-10  

⇒1/v = -1/20 + 1/10 = 1/20  

⇒v = +20cm  

Hence, image position is the 20cm right side from the pole of the concave mirror. The image is straight and bigger than the object.

Explanation:

Sign Convention for Spherical Mirrors,

                                         Concave Mirror                Convex Mirror

      u(object distance)              -                                           -

      v(image distance)              -                                           +

      f(focal length)                     -                                          +