How many lenses with different focal lengths can be obtained by combining two surfaces whose radii of curvature are 4.00 cm and 8.00 cm in absolute magnitude.

The lenses with different focal length are four.

Explanation:

Given that,

Radius of curvature R₁= 4

Radius of curvature R₂ = 8

We know ,

Refractive index of glass = 1.6

When, R₁= 4, R₂ = 8

We need to calculate the focal length of the lens

Using formula of focal length

Put the value into the formula

When , R₁= -4, R₂ = 8

Put the value into the formula

When , R₁= 4, R₂ = -8

Put the value into the formula

When , R₁= -4, R₂ = -8

Put the value into the formula

Hence, The lenses with different focal length are four.

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