Physics · Optics, Nature of Light and Optical Instruments

In this question, we are asked to determine which color of light beam, given the same total energy, would consist of the smallest number of photons. Since the energy of a photon is inversely proportional to its wavelength (E = hc/λ), shorter wavelengths correspond to higher energy. Therefore, violet light, which has the shortest wavelength, will have the highest energy per photon. This means that for a constant total energy, fewer photons are required to make up that energy. Other colors like blue, green, and red have longer wavelengths, resulting in lower energy per photon, thus requiring more photons to equal the same total energy. Hence, the correct answer is violet.

Violet light has the shortest wavelength among the options provided, which means it has the highest energy per photon. Therefore, for the same total energy, fewer photons of violet light are needed.

Blue light has a shorter wavelength than green and red light but longer than violet, implying it contains more photons than violet for the same total energy.

Green light has a longer wavelength than blue and violet, indicating it has lower energy per photon. Thus, it would have more photons than violet for the same total energy.

Red light has the longest wavelength among the options, meaning it has the lowest energy per photon. Therefore, red would contain the largest number of photons for the same total energy, not the smallest.