A combination of a convex lens and a concave lens has a power + 2D. If the focal length of the convex lens is 25 cm, what will be the focal length of the concave lens used in the combination?
Answers
Answered by
2
Power of combination
P=
P
1
+
P
2
⇒
4=
5+
P
2
⇒
P
2
=
4−
5=
−1D
∴
−1=
P
2
=
f(cm)
100
∴
f=
−100cm
Answered by
1
Answer:
-50cm
Explanation:
D=1/f
D=1/0.25
D=4D
Pt=P1+P2
2=4+P2
P2=-2D
F=1/-2
-0.5m or -50cm
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