Question

Two thin lenses (made from same material) of focal
length 12 cm & 8 cm placed co-axially apart. If they
form a achromatic combination, then distance
between them is​

Answer 1

Answer:

The distance between the lenses for the achromatic combination is 10cm.

Explanation:

The distance between the lenses for achromatic combination is given as,

$D=\frac{f_1+f_2}{2}$     (1)

Where,

D=distance between the lenses

f₁=focal length of the first lens

f₂=focal length of the second lens

From the question we have,

f₁=12cm

f₂=8cm

By substituting the values of f₁ and f₂ in equation (1) we get;

$D=\frac{12+8}{2}$

$D=\frac{20}{2}$

$D=10cm$

Hence, the distance between the lenses for the achromatic combination is 10cm.

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