Physics
A convex lens of power +5 D has an object placed at a distance of 50 cm in front of the lens.
(a) State the nature of the image formed.
(b) What is the definite distance, towards or away from the lens, the object should move so that the image is not seen?
Refraction Lens
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Answer
Given, power (P) = +5 D
Object distance = u = -50 cm
Let, image distance = v
Focal length = f =
Focal length = f = +20 cm
Here, object is placed beyond 2F (twice the focal length) of a convex lens, the image will be formed between F and 2F on the opposite side of the lens. Hence, Image is real and diminished.
(b) The object is at 50 cm. If we move the object 30 cm towards the lens, it will be at the focal point (20 cm), so the rays will emerge parallel, and a real image will not be formed.
So, the new position of object = 50 - 30 = 20 cm
∴ The object should be moved 30 cm towards the lens.
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