Which one among the following waves carries the maximum energy per photon ?

The energy of a photon is determined by Planck's equation, E = hf, where energy (E) is directly proportional to the frequency (f) of the electromagnetic wave [6]. Consequently, photon energy is inversely proportional to the wavelength [6]. Within the electromagnetic spectrum, radio waves possess the longest wavelengths and the lowest frequencies, resulting in the lowest energy per photon [1]. Microwaves and visible light waves have progressively higher frequencies and thus higher photon energies than radio waves. X-rays, however, have much higher frequencies and shorter wavelengths compared to visible light, microwaves, and radio waves. As frequency increases across the spectrum from radio to gamma rays, X-rays carry significantly more energy per photon than the other options provided [3]. Therefore, among the choices, X-rays carry the maximum energy per photon.

Sources

1. [4] https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html
2. [6] https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum2.html
3. [1] https://www.sciencedirect.com/topics/neuroscience/electromagnetic-radiation
4. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Explanation: > p. 279