An object of size 3.0 cm is placed 14 cm in front of a concave lens of focal length 21 cm.

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asked Jan 6, 2018 in Physics by sforrest072 (157,439 points) 60 409 933

An object of size 3.0 cm is placed 14 cm in front of a concave lens of focal length 21 cm. Describe the image produced by the lens. What happens if the object is moved further away from the lens?

1 Answer

+1 vote
answered Jan 6, 2018 by mdsamim (213,225 points) 5 10 15
edited Mar 5, 2018 by Vikash Kumar
 
Best answer

Size of the object, h1 = 3 cm 

Object distance, u = −14 cm 

Focal length of the concave lens, f = −21 cm 

Image distance = v 

According to the lens formula, we have the relation:

Hence, the image is formed on the other side of the lens, 8.4 cm away from it. The negative sign shows that the image is erect and virtual. 

The magnification of the image is given as:

Hence, the height of the image is 1.8 cm. 

If the object is moved further away from the lens, then the virtual image will move toward the focus of the lens, but not beyond it. The size of the image will decrease with the increase in the object distance.

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