MCQ Detailed View

Radiant energy is the energy carried by electromagnetic waves. These waves include a wide range of radiation, known as the electromagnetic spectrum, which extends from very high-energy gamma rays to very low-energy radio waves. The energy of electromagnetic radiation depends on its frequency (ν) and wavelength (λ). The relationship is explained by the formula:

E = hν

where E is energy, h is Planck’s constant, and ν is frequency. Higher frequency means higher energy, while lower frequency means lower energy.

At one end of the electromagnetic spectrum are gamma rays, which have extremely short wavelengths and very high frequencies. This makes them the most energetic form of radiation. They are used in nuclear medicine and for killing harmful microorganisms. Slightly lower in energy are X-rays and ultraviolet (UV) rays. UV radiation comes from the Sun and is responsible for tanning and sunburn. In the middle of the spectrum is visible light, which human eyes can detect and which provides the colors we see.

At the opposite end of the spectrum are radio waves. These waves have the longest wavelength and the lowest frequency. Because energy is directly proportional to frequency, radio waves have the lowest energy among all forms of electromagnetic radiation. Despite having very little energy compared to gamma rays, they are extremely useful in everyday life. Radio waves are widely used in radio broadcasting, television signals, mobile communication, radar systems, and satellite communication.

Thus, when we compare gamma rays, ultraviolet rays, visible light, and radio waves, the correct answer is radio waves, because they are the lowest in energy across the electromagnetic spectrum.