For a thin lens with radii of curvatures and R1 and R2 , refractive index n and focal length f , the factor ((1/R1)-(1/R2)) is equal to

Question

For a thin lens with radii of curvatures and R1 and R2 , refractive index n and focal length f , the factor ((1/R1)-(1/R2)) is equal to (A)  (1/f (n-1))  (B)  f (n-1)  (C)  ((n-1)/f)  (D)  (n/f (n-1))

Tardigrade Admin · Accepted Answer

According to lens makerâs formula (1/f)=(n-1) ((1/R1)-(1/R2)) ∴ ((1/R1)-(1/R2))=(1/f (n-1))

Q. For a thin lens with radii of curvatures and $R_{1}$ and $R_{2}$ , refractive index $n$ and focal length $f$ , the factor $(\frac{1}{R _{1}} - \frac{1}{R _{2}})$ is equal to

$\frac{1}{f ( n - 1 )}$

$f (n - 1)$

$\frac{( n - 1 )}{f}$

$\frac{n}{f ( n - 1 )}$

According to lens maker’s formula
$\frac{1}{f} = (n - 1) (\frac{1}{R _{1}} - \frac{1}{R _{2}})$
$∴ (\frac{1}{R _{1}} - \frac{1}{R _{2}}) = \frac{1}{f ( n - 1 )}$

Q. For a thin lens with radii of curvatures and R1​ and R2​ , refractive index n and focal length f , the factor (R1​1​−R2​1​) is equal to

f(n−1)1​

f(n−1)

f(n−1)​

f(n−1)n​