Question

For a lens with \[f = +12\,cm\], \[R_1 = +10\,cm\] and \[R_2 = -15\,cm\], the lens maker's formula \[\frac{1}{f}=(n-1)\left(\frac{1}{R_1}-\frac{1}{R_2}\right)\] gives the refractive index of the glass as:

पर्याय

• \[1.25\]

• \[2.0\]

• \[1.5\]

• \[1.33\]

Answer 1

Substituting the values: \[\frac{1}{12}=(n-1)\left(\frac{1}{10}+\frac{1}{15}\right) = (n-1)\cdot\frac{1}{6}\]. Solving gives \[n - 1 = 0.5\], so \[n = 1.5\].