Question

An object is placed perpendicular to the principal axis of a convex lens of focal length 40 cm. The
distance of the object from the lens is 20 cm.
Find
(i) the position
(ii) the magnification and
(iii) the nature of the image formed

Answer 1

Answer:

(a) If the image formed by a lens is diminished in size and erect, for all positions of the object, the lens is concave. (b) The point on the lens through which a ray of light passes undeviated is the optical centre. (c) Given: Focal length, f= +20 cm Distance of object from lens, u=-30 cm We need to find the distance of image from the lens, v Applying the lens formula Focal length, f- +20 cm Object distance, u = -30 cm Image distance, V= Nature of the image = ? Magnification, m = ? According to lens formula:

V = +60 cm

Thus, magnification is given by

m = 60/-30

m= -2

The image formed is real, inverted and magnified (larger than the object size)

Explanation:

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