A convex lens of focal length 25 cm is in contact with a concave lens of focal length 50 cm. The equivalent focal length of this

Question

2 years ago

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combination-lenses should be Group of answer choices

1 answer:

Gwar [14] · Answer 1 · 2023-03-07T21:02:10+03:00

The equivalent focal length of this combination-lenses should be +50 cm.

Given:

Focal length of convex lens, f₁ = +25 cm

Focal length of concave lens, f₂ = -50 cm

Calculation:

We know that the power of a lens is given as:

P = 1 / f

where, f is the focal length of lens

Now, the power of convex lens can be calculated as:

P₁ = 1/f₁

= 1/(25×10⁻² m)

= 100/25

= +4 D

Similarly, the power of concave lens can be calculated as:

P₂ = 1/f₂

= (1/-50×10⁻² m)

= -100/50

= -2 D

Thus, the power of the combined lenses can be calculated as:

P₍₁₊₂₎ = P₁ + P₂

= +4 D - 2 D

= +2 D

Now, the combined focal length of the lens can be calculated as:

f₍₁₊₂₎ = 1 / P₍₁₊₂₎

= 100 / 2 D

= +50 cm

Therefore, the equivalent focal length of this combination-lenses will be +50 cm.

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