American Board of Ophthalmology (ABO) Practice Exam

What does the wave-particle duality of light signify?

1. Light can only behave as a wave.

2. Light can only behave as a particle.

3. Light displays both particle and wave behavior.

4. Light cannot be classified as either a wave or a particle.

The correct answer is: Light displays both particle and wave behavior.

The wave-particle duality of light signifies that light exhibits both particle and wave characteristics, which is at the core of quantum mechanics. This concept was developed to explain phenomena that could not be understood by considering light solely as a wave or a particle. When light is described as a wave, it shows properties such as interference and diffraction, which are characteristic of waves. For example, when light passes through narrow slits, it creates patterns on a screen that demonstrate its wave nature through constructive and destructive interference. Conversely, light can also be understood in terms of particles, known as photons. This perspective is crucial when discussing interactions of light with matter, such as the photoelectric effect, where photons are absorbed by electrons in materials, causing them to be ejected. This behavior aligns with classical particle physics and suggests that light has quantized energy levels. The ability of light to demonstrate both behaviors depending on the experimental setup confirms the duality concept. Thus, the correct choice highlights this fundamental principle of physics, showcasing the complexity of light's true nature in the framework of quantum mechanics.