Power of convax lens is 5 D and the power of concave lens is 2 D. What...
You may know that the power of convex lens is in (+) and that of concave is in (-).
here we have:-
power of convex lens= +5D and
power of concave lens= -2D
So, power of combination will be:-
power of convex lens + power of concave lens
=+5D + (-2D)
=+3D
hence option D(+3D) is correct answer..
Thank you.. :-)
Power of convax lens is 5 D and the power of concave lens is 2 D. What...
Combination of Convex and Concave Lenses
Given that the power of the convex lens is 5 D and the power of the concave lens is 2 D. We need to find out the power of the combination of these lenses when placed in contact.
Formula for calculating the power of a lens
The power of a lens is given by the formula:
P = 1/f
Where P is the power of the lens in dioptres (D) and f is the focal length of the lens in meters.
Calculating the focal length of the convex lens
We know that the power of the convex lens is 5 D. Let us assume that the focal length of the convex lens is f1.
Using the formula for calculating the power of a lens, we get:
5 = 1/f1
f1 = 1/5
f1 = 0.2 m
Calculating the focal length of the concave lens
We know that the power of the concave lens is 2 D. Let us assume that the focal length of the concave lens is f2.
Using the formula for calculating the power of a lens, we get:
-2 = 1/f2
f2 = -1/2
f2 = -0.5 m
Calculating the power of the combination of lenses
When the two lenses are placed in contact, the effective focal length of the combination is given by:
1/f = 1/f1 + 1/f2
Substituting the values of f1 and f2, we get:
1/f = 1/0.2 - 1/0.5
1/f = 5 - 2
1/f = 3
Therefore, the power of the combination of lenses is:
P = 1/f
P = 1/3
P = 0.33 D
Hence, the correct answer is option D, i.e., 3 D.
To make sure you are not studying endlessly, EduRev has designed Class 10 study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Class 10.