Which of the following types of radiation has the highest photon energy?
2014
Which of the following types of radiation has the highest photon energy?
- A.
Ultraviolet rays
- B.
X-rays
- C.
Infrared rays
- D.
Gamma rays
Show answer & explanation
Correct answer: D
CONCEPT: For electromagnetic radiation, the energy carried by each photon is given by E = hf, where h is Planck's constant and f is the frequency; since frequency and wavelength are related by c = fλ, photon energy rises as frequency increases and wavelength shortens.
APPLICATION:
Radiation type | Typical wavelength range | Relative frequency |
|---|---|---|
Infrared rays | about 700 nanometres to 1 millimetre | Lowest |
Ultraviolet rays | about 10 to 400 nanometres | Low |
X-rays | about 0.01 to 10 nanometres | High |
Gamma rays | less than about 0.01 nanometres | Highest |
A shorter wavelength corresponds to a higher frequency. Applying E = hf, the radiation with the highest frequency in the table above carries the greatest photon energy — that is gamma rays.
CROSS-CHECK: Using E = hc/λ, energy is inversely proportional to wavelength. Gamma rays have the shortest wavelength of the four (originating from nuclear transitions rather than atomic or thermal processes), which independently confirms that gamma rays carry the maximum energy among the options.