Which one among the following has largest energy per photon?

The energy of a photon is directly proportional to its frequency and inversely proportional to its wavelength, as defined by the relation E=hf [3]. In the electromagnetic spectrum, radiation types are ordered by increasing frequency and energy as follows: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays [1]. Among the given options, X-rays possess the highest frequency and the shortest wavelength (approximately 0.01 to 10 nm), resulting in the largest energy per photon. Ultraviolet rays have lower energy than X-rays but higher than visible light, while infrared radiation has the lowest energy among the choices provided [1][2]. Consequently, X-rays are the most energetic photons in this list, often measured in hundreds of electron volts (eV) compared to the few eV of ultraviolet or visible light [1].

Sources

1. [3] https://en.wikipedia.org/wiki/Electromagnetic_spectrum
2. [1] https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html
3. [2] https://en.wikipedia.org/wiki/Photon_energy