If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together, what will be their resultant power ?

Step-by-step solution

f₁=+80 ~cm , f₂=-50 ~cm . Resultant focal length aligned F & = f₁ f₂ f₁+f₂ & = 80 -50 80-50 = -4000 30 & =- 4000 3 ~cm . aligned Resultant power aligned P & = 100 F = 100 -400 / 3 & =- 3 4 & =-0.75 D . aligned