Optical power from thin lens radii and refractive indices
=========================================================

Optical power of a thin lens can be calculated from the radii of its front and back
surfaces and the refractive indices of the lens material and the medium.

**Links:**

#. `Wikipedia, definition of optical power <https://en.wikipedia.org/wiki/Optical_power>`__.
#. `Wikipedia, formula for effective focal length <https://en.wikipedia.org/wiki/Lens#Thin_lens_approximation>`__.

..
    TODO add info about the sign convention for radii

.. py:currentmodule:: symplyphysics.laws.optics.optical_power_from_thin_lens_radius

.. py:data:: optical_power

    :attr:`~symplyphysics.symbols.optics.optical_power` of the lens.

Symbol:
    :code:`D`

Latex:
    :math:`D`

Dimension:
    :code:`1/length`


.. py:data:: lens_refractive_index

    :attr:`~symplyphysics.symbols.optics.relative_refractive_index` of the lens material.

Symbol:
    :code:`n`

Latex:
    :math:`n`

Dimension:
    :code:`dimensionless`


.. py:data:: medium_refractive_index

    :attr:`~symplyphysics.symbols.optics.relative_refractive_index` of the surrounding medium.

Symbol:
    :code:`n_0`

Latex:
    :math:`n_{0}`

Dimension:
    :code:`dimensionless`


.. py:data:: front_radius

    :attr:`~symplyphysics.symbols.classical_mechanics.radius` of the front surface.

Symbol:
    :code:`r_1`

Latex:
    :math:`r_{1}`

Dimension:
    :code:`length`


.. py:data:: back_radius

    :attr:`~symplyphysics.symbols.classical_mechanics.radius` of the back surface.

Symbol:
    :code:`r_2`

Latex:
    :math:`r_{2}`

Dimension:
    :code:`length`


.. py:data:: law

    :code:`D = (n - n_0) * (1 / r_1 - 1 / r_2)`


    Latex:
        .. math::
            D = \left(n - n_{0}\right) \left(\frac{1}{r_{1}} - \frac{1}{r_{2}}\right)