Do light waves bend around obstacles and through openings? If they do, then it would provide still more evidence to support the belief that light behaves as a wave. When light encounters an obstacle in its path, the obstacle blocks the light and tends to cause the formation of a shadow in the region behind the obstacle. Light does not exhibit a very noticeable ability to bend around the obstacle and fill in the region behind it with light.
Nonetheless, light does diffract around obstacles. In fact, if you observe a shadow carefully, you will notice that its edges are extremely fuzzy. Interference effects occur due to the diffraction of light around different sides of the object, causing the shadow of the object to be fuzzy. This is often demonstrated in a Physics classroom with a laser light and penny demonstration.
Light diffracting around the right edge of a penny can constructively and destructively interfere with light diffracting around the left edge of the penny. The result is that an interference pattern is created; the pattern consists of alternating rings of light and darkness. Such a pattern is only noticeable if a narrow beam of monochromatic light i. The photograph at the right shows an interference pattern created in this manner. Since, light waves are diffracting around the edges of the penny, the waves are broken up into different wavefronts that converge at a point on a screen to produce the interference pattern shown in the photograph.
Can you explain this phenomenon with a strictly particle-view of light? This amazing penny diffraction demonstration provides another reason why believing that light has a wavelike nature makes cents I mean "sense". These interference effects will be discussed in more detail later in this lesson. Light behaves as a wave - it undergoes reflection, refraction, and diffraction just like any wave would.
In this case, you could say that height is quantized. The same is true for a particle in a box or an electron in a hydrogen atom. There are only certain possible energy levels.
Does this quantum energy model agree with classical mechanics? If you looked at a tennis ball bouncing back and forth in a typical classroom, you could calculate the quantized energy levels. However, these energy levels are so close to each other that you essentially would never be able to experimentally verify that the ball can only have certain energy levels. Just to be clear: the quantum model of stuff is just like the other models above.
It slowly gives a different result from the classical model of stuff. You have been very patient. I know you want to talk about photons, but I had to get the model stuff out of the way. But like I said, just about every introductory physics textbook talks about photons using the photoelectric effect as a basis for this model. There is a reason for this. Albert Einstein won the Nobel Prize in in part for his explanation of the photoelectric effect. Of course, Einstein did some other awesome stuff.
In particular, the general and special theory of relativity. But here is the crazy part I know, you probably think this whole post is crazy : the photoelectric effect can be explained with a classical wave model of light along with a quantum model of matter. Really, it can. Skipping the details, let me just say and you can look in your quantum mechanics book to verify this that if you have a particle with energy E1 and you want it to transition to the energy level E 2 you can do that by adding a time-varying potential such that:.
That looks strangely similar to the equation for the energy of a photon. If you like, you can use light with a frequency of f to induce the transition from one energy level to another. This oscillating perturbation can explain both absorption AND emission of light. What about the photoelectric effect? Physicists describe light as both a particle and a wave. In fact, light's wavelike behavior is responsible for a lot of its cool effects, such as the iridescent colors produced on the surface of bubbles.
To see a dramatic and mind-bending example of how light behaves like a wave, all you need is three pieces of mechanical pencil lead, a laser pointer and a dark room. Background Sound is a great example of a wave that propagates, or travels, much like ripples in a pond do.
In both cases kinetic energy flows through matter without permanently displacing the molecules in the matter itself—instead, it puts the matter through phases of compression where the molecules get pushed together and rarefaction where the molecules spread apart. Think of the inside of a speaker vibrating with the music.
When waves come into contact with one another, they exhibit interference: waves that are all in phase rarefying or compressing the same particles at the same time add together to become stronger, and waves that are out of phase with one another for example, one wave attempts to rarefy particles in a medium while another attempts to compress those same particles cancel out.
This is how noise-canceling headphones work—they produce a sound wave that resembles the wave responsible for the unwanted sound, but with the original phases of rarefaction and compression flipped. This has the effect of dampening the offending sound wave's effect on the air molecules. So that by the time its energy reaches your ear, the sound you perceive is more of a whisper than a shout—or an airplane engine's roar is more like a quiet hum.
Diffraction is another important feature of waves: When waves encounter small openings, they spread out after they pass through. In the following experiment we'll set up two slits to give waves of light the opportunity to diffract as they travel through them. The different points at which the diffracted waves overlap should demonstrate some cool patterns of constructive and destructive interference, and you'll get to witness the puzzling effect of light "canceling itself out.
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Commenters, please keep in mind that comments should be used for suggesting improvements and requesting clarification on the question, not for answering. Add a comment. Active Oldest Votes. To address your question, we could just as well ask the question like this: In order for a wave to propagate, there either has to be some restoring force, or there has to be a way for one "unit" of the wave to push or pull on the next unit of the wave.
Improve this answer. The behaviour of light depends on the size of the slit compared to its wave lenght. Claudio Saspinski Claudio Saspinski 9, 2 2 gold badges 10 10 silver badges 25 25 bronze badges. Some diffracting and some not so much. PhysicsDave PhysicsDave 1, 6 6 silver badges 9 9 bronze badges. Superfast Jellyfish Superfast Jellyfish 8, 3 3 gold badges 17 17 silver badges 40 40 bronze badges.
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