Do photons really bounce and bend? A question for physicists

In summary: Huygen's principle is a way of thinking about the wave-like behavior of particles. It's similar to Born2bwire's description of how waves cause currents on and inside objects. However, Huygen's principle goes a step further and says that the wave-like behavior of particles can be completely explained by the collective action of their individual waves.
  • #1
curioso
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I am not a physicist but I do have a non-mathematical science background and I am a serious physics appreciator. I am new to this site and have a pressing question I would like to ask a physicist.

High school and even college level physics texts desribe the reflection and refraction of light as bouncing and bending phenomena respectively. But how can this be? At the quantum level do photons really "bounce" off of electron clouds -- and do the paths of individual photons really "bend" as they move from one transparent medium into another. I find this a little hard to swallow.

Are these phenomena not really absorption and re-emission events?

Thanks.
 
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  • #2
It's hard to describe the exact mechanisms but in general it's just generic wave physics. Waves, when incident upon various boundaries, exihibit interference, reflection, refraction, diffraction and probably some other -ractiony things.

Part of this has to do with the interaction of the boundary with the wave. For example, if a sound wave hits a wall, the wall actually will vibrate. If an electromagnetic wave hits a conductive surface, it will induce currents on and inside the surface. These effects are sources for secondary waves. The combination of the incident wave and these secondary waves gives rise to the total wave that you observe. So if you consider that incident waves create sources on and inside objects, you can get a better sense for how these waves can bend around corners; because there are waves being created throughout the object. Cancellation of the secondary and incident fields arise due to constructive and destructive interference. This is how reflection occurs. The incident wave constructively interferes with the secondary wave in front of the boundary. But inside and behind the boundary the two destructively interfere. The end result is that there are no waves inside or behind the boundary but there is a reflected wave in front of it.

Photons will exhibit the same basic wave phenomenon. We can observe in experiments even single photons interfering with themselves or diffracting through slits and so forth. However, modern quantum theories do not consider the photon to have a physical path. At best, we talk about being certain of a photon being sourced at point A and being absorbed (say by measurement of a detector) at point B. How the photon behaves between its creation and annihilation is undefined. In fact, if we were to have a series of detectors that observed the path of the photon from A to B, we would destroy the quantum effects. For example, as I mentioned before, we can see single photon interference in a double slit experiment. However, if we were to detect which slit the photon passed through, we destroy the interference (but we still get diffraction).
 
  • #3
Dr, Mr or Ms Born2bwire...

Thanks for this. It gives me lots to ponder!

Curioso
 
  • #4
Huygen's principle is also another way of looking at it too. An analog of this is often used in computational methods. For example, we will decompose the excited currents on the surface of a metal as being the combination of many small current sources. Individually, these current sources will look like spherical wave sources. But because of how the individual waves interfere, the summation of the waves from all the current sources will be the total excited wave.
 
  • #5
Born2bwire

Thanks again. I'm not familiar with Huygen's principle. I'll have to check that out. What you've said about wave induction of currents, secondary waves, interference etc. computes for me. Will continue to ponder.

Curioso
 

1. What is the difference between reflection and refraction?

Reflection is the bouncing back of light or other waves off a surface, while refraction is the bending of light as it passes through a medium.

2. How are reflection and refraction related?

Reflection and refraction are two properties of light that occur when it interacts with a surface or medium. They are both caused by the change in speed and direction of light as it moves from one medium to another.

3. What is the law of reflection?

The law of reflection states that the incident angle of a light ray is equal to the angle of reflection, and both angles are measured from the normal line at the point of incidence.

4. What factors affect the amount of reflection and refraction of light?

The amount of reflection and refraction of light is affected by the angle of incidence, the properties of the surface or medium, and the wavelength of the light.

5. How is refraction used in everyday life?

Refraction is used in everyday life in various ways, such as in eyeglasses and contact lenses to correct vision, in microscopes and telescopes to magnify objects, and in the design of optical instruments like cameras and projectors.

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