# what property of an EM wave describes its energy or how powerful it is?

what property of an EM wave describes its energy or how powerful it is?

In: Physics

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The energy of a photon is proportional to its frequency (inversely proportional to its wavelength). High frequency, high energy. That’s why x-rays and gamma-rays are much more dangerous than radio.

But you also have to consider intensity (amplitude of the EM wave). You can think of that as having more photons present. Bright sunlight (greater intensity) will give you a sunburn faster than very dim sunlight.

This can be explained by [Photon Energy](https://en.wikipedia.org/wiki/Photon_energy) and the equation E = (h * c) / λ.

E is the Energy of the EM wave

λ is the distance of the wavelength

h is the Planck Constant (6.626*10^-34 Joule*second or 4.136*10^-15 electron volt*second)

c is the speed of light in a vacuum (2.998*10^8 meter/second)

This means that the energy of light is inversely proportional to the wavelength of the light (shorter wavelength = higher energy)

Also, since you can describe the frequency of an EM wave as *ν* = c/λ, that means that a wave’s energy is directly proportional to its energy (higher frequency = higher energy)

Energy is determined by the frequency of the wave. The higher the frequency, the more energetic. That means that energy is also inversely related to wavelength (longer wavelength equals lower energy) since the speed of light is equal to wavelength times frequency.