Evidence for wave and particle properties of light

[kitkat]

I am really stuck on this problem.

What evidence supports the notion that light has wave properties? What evidence supports the view that light has particle properties?

I know that the Quantum theory tells us that both light and matter consists of tiny particles which have wavelike properties associated with them but I am still unsure what is being asked...Any advice?

Kat

 

[topsquark]

I am really stuck on this problem.

What evidence supports the notion that light has wave properties? What evidence supports the view that light has particle properties?

I know that the Quantum theory tells us that both light and matter consists of tiny particles which have wavelike properties associated with them but I am still unsure what is being asked...Any advice?

Kat

The best evidence for light as a wave is Young's double slit experiment. Shine a monochromatic light beam (a laser works nicely) at two thin slits separated by a large distance (relative to the slit size). Projected onto a screen in the background we get a diffraction pattern...a hallmark of waves.

The best evidence (I believe) for light as a particle is either Compton scattering or the photo-electric effect. In Compton scattering an x-ray is scattered off a free electron; the results imply a particle collision. In the photo-electric effect light is introduced to a metal surface, which then ejects electrons. The manner in which the electrons are ejected (the energy of the electrons depend on the frequency of the light, not the intensity) also imply a particle model.

Of course, quantum says they are neither. Quantum "particles" have either wave-like or particle-like properties depending on which experiment we do. Any experiment will detect one type of property or the other, but not both. If that confuses you, you are in good company. No one else really understands it either, almost 100 years after the concept was introduced.

-Dan

 

[kyle8921]

rina, it is understandable that you are feeling stuck on this problem. The concept of light having both wave and particle properties can be a difficult one to grasp. Let's break it down and look at the evidence for each aspect separately.

First, let's consider the evidence for light having wave properties. One of the earliest experiments that demonstrated this was the double-slit experiment conducted by Thomas Young in the early 1800s. In this experiment, a beam of light was shone through two narrow slits and the resulting pattern on a screen behind the slits showed interference, similar to what would be seen with two overlapping water waves. This interference pattern could only be explained by light behaving as a wave. Additionally, other phenomena such as diffraction and polarization also support the wave nature of light.

On the other hand, there is also evidence for light having particle properties. This was first proposed by Max Planck in the late 1800s and was further developed by Albert Einstein with his theory of the photoelectric effect. This experiment showed that light can also behave as individual particles, known as photons, which have discrete energy levels and can interact with matter in a particle-like manner. Additionally, the Compton effect, where X-rays are scattered by electrons, also supports the particle nature of light.

It is important to note that both wave and particle properties of light are necessary to fully understand its behavior. The duality of light is a fundamental concept in quantum mechanics and has been confirmed by numerous experiments. I hope this helps to clarify the evidence for both aspects of light's nature and how they work together.