The size of the image of an object, which is at infinity, as formed by a convex lens of focal length $$30$$ cm is $$2$$ cm. If a concave lens of focal length $$20$$ cm is placed between the convex lens and the image at a distance of $$26$$ cm from the convex lens, calculate the new size of the image

Question

Infinity Learn · Accepted Answer

Convex lens will form image $$I1$$, at its focus which acts like a virtual object for concave lens.Hence for concave lens u $$=$$ $$+$$ $$4$$ cm, f $$=$$ $$20$$ cm. So by lens formula $$1$$−$$20=1v$$−$$14$$⇒$$v=5$$ cm  i.e.,  distance   of  final   image  $$I3$$ from  concave  lens  $$v=5$$  cm  by  $$usingvu=IO$$⇒$$54=I2$$⇒$$I2=2.5$$  cm

The size of the image of an object, which is at infinity, as formed by a convex lens of focal length 30 cm is 2 cm. If a concave lens of focal length 20 cm is placed between the convex lens and the image at a distance of 26 cm from the convex lens, calculate the new size of the image

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