A concave lens is kept in contact with a convex lens of focal length 20cm the combination works as a converging lens of focal length 100cm calculate the power of concave lens
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Answered by
88
Let :
f₁ = focal length of the concave lens.
f₂ = focal length of the convex lens
F = The combined focal length.
Then :
1/F = 1/f₁ + 1/f₂
F = 100cm
f₂ = 20 cm
1/100 = 1/f₁ + 1/20
1/f₁ = 1/100 - 1/20
1/f₁ = - 1/25
f₁ = - 25cm
The negative sign indicates that the image formed by this lens is virtual.
Power = 1/f₁
= 1/25 = 0.04
= 0.04
Answered by
24
Answer:
Explanation:
f₁ = focal length of the concave lens.
f₂ = focal length of the convex lens
F = The combined focal length.
Then :
1/F = 1/f₁ + 1/f₂
F = 100cm
f₂ = 20 cm
1/100 = 1/f₁ + 1/20
1/f₁ = 1/100 - 1/20
1/f₁ = - 1/25
f₁ = - 25cm
The negative sign indicates that the image formed by this lens is virtual.
Power = 1/f₁
= 1/25 = 0.04
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