Added Photoelectric effect equation (#9666)

* Added Photoelectric effect equation

Photoelectric effect is one of the demonstration of quanta of energy.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fixed doctest

Co-authored-by: Rohan Anand <[email protected]>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Rohan Anand <[email protected]>