# Physics - Electromagnetic Radiation

> Source: https://ollybritton.com/notes/a-level/physics/topics/electromagnetic-radiation/ · Updated: 2021-05-24 · Tags: school, quantum, year-1

## See Also
- [Physics - Quantum Physics](https://ollybritton.com/notes/a-level/physics/topics/quantum-physics/)
- [Physics - The Photoelectric Effect](https://ollybritton.com/notes/a-level/physics/topics/photoelectric-effect/)

## Flashcards
##### What is the equation for the energy of a photon in terms of frequency??
$$
E = hf
$$

##### What is the equation for the energy of a photon in terms of wavelength??
$$
E = \frac{hc}{\lambda}
$$

##### What is the approximate value of $h$, Plank's constant??
$$
6.63 \times 10^{-34}
$$

##### What unit is commonly used for the energy on a photon??
Electronvolts, $eV$s.

##### Why might the efficiency of a photodiode be less than 100%??
* Some photons are not absorbed
* Some photons are reflected

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