section_path: Construction of simple lenses/Lensmaker's equation/Thin lens approximation
section_name: Thin lens approximation
paragraph_text: Thin lens approximation
  
  If d is small compared to R and R then the thin lens approximation can be made. For a lens in air, f is then given by
  
  1 f ≈ (n − 1). {\displaystyle {\frac {1}{\ f\ }}\approx \left(n-1\right)\left\,.}