If two + 5 D , lenses are mounted at some distance apart, the equivalent power will always be negative, if the distance is

Question

If two + 5 D , lenses are mounted at some distance apart, the equivalent power will always be negative, if the distance is, Greater than 40 cm, Equal to 10 cm, Greater than 8 0 cm, Less than 10 cm

MARKS App · Accepted Answer

When two lenses are separated by some distance x , then equivalent power P = P ₁ + P ₂ - x P ₁ P ₂ ∴ P = 5 + 5 - x × 5 × 5 o r P = 10 - 25 x Power P will be negative if 10-25x will be negative i e , 25 x > 10 o r x > 10 25 o r x > 10 25 × 100 cm o r x > 40 cm

Search any question & find its solution

Looking for more such questions to practice?