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Question : 11
Total: 12
A 6 cm 30 cm 45 cm
OR
An object6 cm 50 cm 30 cm
At what distance from the lens should a screen be placed in order to obtain a sharp image of the object? Find the nature and size of the image. Also draw labelled ray diagram to show the image formation in this case.
OR
An object
At what distance from the lens should a screen be placed in order to obtain a sharp image of the object? Find the nature and size of the image. Also draw labelled ray diagram to show the image formation in this case.
Solution:
Given, Height of the object h 0 = 6 cm
Focal length,f = − 30 cm
Object distance,u = − 45 cm
Image distance,v =
Height of image,h i =
We have,
=
+
=
+
+
=
=
v = − 90 cm
Also, we have
m =
=
=
= − 2
h i = − 12 cm .
Image is real and inverted.
Height of objecth o = + 6 cm u = − 50 cm f = + 30 cm ( C ) ( F ′ )
Using lens formula,
=
−
=
+
=
−
=
=
∴ v = + 75 cm
=
=
h i =
= − 9 cm
Hence, image formed is virtual, erect and magnified.
Focal length,
Object distance,
Image distance,
Height of image,
We have,
Also, we have
Image is real and inverted.
OR
Height of object
Formation of image by a convex lens when the object is placed between its optical centre
Using lens formula,
Hence, image formed is virtual, erect and magnified.
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