The focal length of double concave lens kept in air with two spherical surfaces of radii R1 = 30 cm and R2 = 60 cm 

Monjur Alahi

The focal length of double concave lens kept in air with two spherical surfaces of radii R1 = 30 cm and R2 = 60 cm 

A) 40 cm 

B) – 40 cm 

C) 20 cm 

D) – 20 cm


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Salim Ahmed Kawsar

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Correct option is  B) – 40 cm

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