The focus distance of a convex lens is 20 cm. At what distance from this lens should an object be placed so that its image is made 2 times larger than the object, while the image is real?
Answers
Answered by
153
Solution :-
Focal length of the convex lens f = 20 cm
Given :
The image formed is 2 times larger than the object
Therefore, Magnification m = - 2
[ 2 is taken as negative since the image is real ]
Also, Magnification m = v/u
⇒ - 2 = v/u
⇒ - 2u = v
⇒ v = - 2u
Now, by using lens formula
Substituting f = 20 and v = - 2u
Therefore the object is placed 30 cm from the convex lens.
Answered by
117
Answer:
Explanation:
Given that there is a convex lens.
- focal length, f = 20 cm
Since, the image is real, therefore magnification will be negative.
.°. Magnification, m = -2
Let us imagine that
- Object distance = u
- Image distance = v
Also, we know that ,
Substituting the values, we get
Now , from lens formula, we have
Again, substituting the values, we get
Hence, object should be placed at a distance of 30 cm from the optical center of the convex lens.
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