Convex lens of 10 cm focal length is combined with a concave lens of 6 cm focal length. Find focal length of combination.
Answers
1/f=(1/f1)+(1/f2)
1/f=(1/10)-(1/6)
1/f=(6-10)/60
1/f=-4/60
f=-60/4
f=-15
Answer:
Explanation:
Definition of convex lens:
The center of this kind of lens is thicker than the edges. Two spherical surfaces often make up an optical lens. The lens is referred to as a biconvex lens or just a convex lens if those surfaces are curved outwards. These lenses have the ability to focus an outside light beam to a spot on the opposite side by converging it. The focal length of a convex lens is the measurement from the lens's center to the focus. This point is known as the focus. A plano-convex lens, on the other hand, is one in which one of the surfaces is flat and the other convex.
Definition of concave lens:
A concave lens is one that bends a straight light beam away from the source and focuses it into a distorted, upright virtual image. Both actual and virtual images can be created using it. At least one internal surface of concave lenses is curved. Since it is rounded at the center and bulges outward at the borders, a concave lens is also known as a diverging lens because it causes the light to diverge. Since they make distant objects appear smaller than they actually are, they are used to cure myopia.
Given:
convex lens=10 cm
concave lens=6 cm
Find:
focal length of their combination.
Solution:
As is common knowledge, convex lenses' focal lengths are positive while concave lenses' focus lengths are negative.
The focal length of their combination is given by
1/f=(1/f1)+(1/f2)
1/f=(1/10)-(1/6)
1/f=(6-10)/60
1/f=-4/60
f=-60/4
f=-15
Hence focal length of their combination= -15
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