Question

The principal axis of a convex lens is along x axis the coordinate of a point object and its image are -20 cm,2cm and25cm,-4cm respectively. The focal length of lens is

Answer 1

The lens formula is as follows :

1/f = 1/u + 1/v

f = focal length

u = Image distance

v = Object distance

Now :

u = 25cm

v = -20 cm

We want f:

1/f = 1/25 - 1/20

1/f = -1/100

Focal length = -100cm

Answer 2

Focal length: The distance between the center of a lens and its focus is called the focal length.

Given:

X axis coordinate of the object (-20cm, 2cm)

X axis coordinate of the image (25cm, -4cm)

Solution:

According to lens formula,

1 / f = 1 / v - 1 / u

The distance of object distance u = -20 cm

The distance of image distance v = 25 cm

The focal length,

f = ( u v ) / ( u - v )  

f = ( - 20 x 25 ) / ( -20 - ( -25 ) )  

f ≅ 10cm

Hence, the focal length is 10 cm.

Read more on Brainly.in - https://brainly.in/question/6430826