where

u = object distance [cm]

v = image distance [cm]

f = focal length of lens [cm]

When applying the equation, take note of the following:

1) The object distance,

__u__

__, is always positive.__

2) If the image on the same side of the lens as the light leaves the lens. Then v is positive and the image is real .

3. If the image on the same side of the lens as the light rays enter the lens. Then v is negative

and the image is virtual.

Worked example :

1. An object of height 3 cm is placed

(a) at 30 cm

(b) at 5 cm

from a convex lens of focal length 10 cm. determine the position and the size of the image in each case.

solution :

given ,

u= 30 cm, f = 10 cm

find v=?

1/f = 1/u + 1/v

1/10 = 1/30 + 1/v

v= +15 cm

(a positive sign shows that the image is real )

m = image height / object height = v/u

image height / 3 = 15/30

==> image height =1.5 cm

The image is real and at the distance of 15 cm from the lens on the opposite side of the object. the height of the image is 1.5 cm.

## 0 comments:

## Post a Comment

Note: Only a member of this blog may post a comment.