Question

two lenses of focal length is 8 cm and 4 cm are placed at a certain distance apart. calculate the distance between if the lenses is form a acromatic combination

Answer 1

Hey mate

here's your answer

The combination of the focal length is 4 cm.

Explanation:

Given that,

Focal length f_{1} = 4\ cm

Focal length f_{1} = 4\ cm

Distance d = 8 cm

The combination of the focal length is defined as:

\dfrac{1}{f_{eq}}=\dfrac{1}{f_{1}}+\dfrac{1}{f_{2}}-\dfrac{d}{f_{1}f_{2}}

\dfrac{1}{f_{eq}}=\dfrac{1}{4}+\dfrac{1}{8}-\dfrac{4}{4\times8}

\dfrac{1}{f_{eq}}=\dfrac{1}{4}

f_{eq}=4\ cm

Answer 2

Given : Two lenses of focal length is 8 cm and 4 cm are placed at a certain distance apart.

To find : The distance between lenses if lenses is a form of acromatic combination.

solution : let distance between two lenses is d.

The condition for acromatic combination,

d = (f₁ + f₂)/2

where f₁ and f₂ are focal lengths of lenses.

here, f₁ = 8 cm , f₂ = 4cm

so, d = (8cm + 4cm)/2 = 6cm

Therefore distance between lenses is 6 cm.

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