Using the lensmaker's formula (equation (5) of your lab manual), calculate the index of refraction of the acrylic lens. You should use the f_are you calculated in part (1) above instead of the value for the focal length of the concave lens that you measured. Remember that the focal length of a concave lens is negative so in this case, f = -f_are.

  n = 1 + R / f

Explanation:

The equation of the constructor is optical is

          1 / f = 1 / p + 1 / q

where f is the focal length, p and q are the distance to the object and image, respectively

The exercise tells us that it is a concave lens with focal length fo, in these lenses the focal length is negative. The relationship to calculate the focal length is

         1 / f = (n -n₀) (1 /R₁ - 1 /R₂)

where is n₀ the refractive index of the medium that surrounds the lens in this case it is air with n₀ = 1, you do not indicate the type of lens, but the most used lens is the concave plane, in this case R₂ = ∞, so which 1 / R₂ = 0, let's substitute

         1 / f = (n-1) / R₁

         n - 1 = R₁ / f

let's calculate

         n = 1- R₁ / f

remember that the radius of curvature is negative, so the equation is

         n = 1 + R / f