Focal length of a concave spherical mirror
==========================================

The focal length of a spherical mirror is equal to half the radius of curvature.

**Notes:**

#. For a concave mirror, the focal length is positive.
#. For a convex mirror, the focal length is negative.

**Conditions:**

#. The :ref:`Small-angle approximation <small_angle_def>` is assumed.

**Links:**

#. `Spherical mirrors <https://phys.libretexts.org/Bookshelves/University_Physics/University_Physics_(OpenStax)/University_Physics_III_-_Optics_and_Modern_Physics_(OpenStax)/02%3A_Geometric_Optics_and_Image_Formation/2.03%3A_Spherical_Mirrors>`__.

.. py:currentmodule:: symplyphysics.laws.optics.focal_length_of_a_concave_spherical_mirror

.. py:data:: focal_length

    Mirror's :attr:`~symplyphysics.symbols.optics.focal_length`

Symbol:
    :code:`f`

Latex:
    :math:`f`

Dimension:
    :code:`length`


.. py:data:: curvature_radius

    Mirror's :attr:`~symplyphysics.symbols.basic.radius_of_curvature`

Symbol:
    :code:`r`

Latex:
    :math:`r`

Dimension:
    :code:`length`


.. py:data:: law

    :code:`f = r / 2`


    Latex:
        .. math::
            f = \frac{r}{2}