# Given photon with a photon energy of 2 eV how calculate the wave length?

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The energy of a photon is *`E=hf` *, where *f* is the frequency of radiation and *h* is the Plank constant `h = 4.1 * 10^(-15) eV*s`

The frequency and the wavelength `lambda` are connected by the relationship

`f = c/lambda` , where *c *is the speed of light `c=3*10^8 m/s`

So, `E = (hc)/(lambda)` and `lambda = (hc)/E = (4.1*10^-15 * 3* 10^8 m)/2` = `6.1*10^-7 m = 600 nm`

**The wavelength of a 2 eV photon is 600 nanometers.**

**Sources:**