Waves

[hansen44]

I was wondering is there any relation to waves, frequency, and intensity. If you increase the frequency of a wave does that increase the intensity of the wave? What is the relation between wavelength and intensity. Also how do these concepts apply to particles. Is the relation E=(frequency)(wavelength) for particles, correct?

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[physics junkie]

I was wondering is there any relation to waves, frequency, and intensity. If you increase the frequency of a wave does that increase the intensity of the wave? What is the relation between wavelength and intensity. Also how do these concepts apply to particles. Is the relation E=(frequency)(wavelength) for particles, correct?

I can see you haven't researched your questions at all by yourself. This is going to make it difficult to answer you clearly. Read your review material on waves first and then formulate more specific questions. And ALWAYS do a search on the forum first before posting.

You're asking quantum physics questions if you want to know how wave physics applies to particles. Basically DeBroglie realized that every particle can be described by a wave and different properties of the wave correspond to different physically observable characteristics of a particle. So the example of this you're asking about is how the energy can be determined from the wavelength. In quantum physics the energy of a wave is given by E=hf where h is planck's constant and f is the frequency of the wave. The frequency 'f' of the wave can be calculated from the wavelength using the formula c=frequency*wavelength where 'c' is the speed of light.

Side note: De Broglie also said that wavelength = h/mv. You don't need to know that but what's interesting is that for any particle you can calculate a wavelength for it. And sure enough the particle actually exhibits properties of a wave...the most obvious being diffraction. These effects are impossible to observe on distance scales that we're used to but they are real. Essentially both the idea of a particle and a wave are inaccurate to describe matter. Matter exhibits properties of both particles and waves.

Wave intensity is defined as the average amount of energy transported by a wave in the direction of wave propagation, per unit area per unit time. Sound intensity can be learned about here:http://hyperphysics.phy-astr.gsu.edu/Hbase/sound/intens.html or on wikipedia. The intensity of an electromagnetic wave is given by the Poynting vector(http://en.wikipedia.org/wiki/Poynting_vector) but you don't need to know that for the MCAT. You could reason that because increasing the frequency of a wave increases it's energy that increasing the frequency increases the intensity. The intensity of an electromagnetic wave is given by

 

[hansen44]

Thank you for all your effort. As a matter of fact though I have read the review chapters front to back numerous times and have studied physics for years. The reason I asked such a broad question was because of an answer on a practice exam that dealt with these concepts. After getting the answer wrong I was puzzled about the answer it went against the fundamental properties which you simply described. Therefore, I pursued a second opinion to reinforce my knowledge and understanding of the topic. Do not assume because I ask such broad questions I am ignorant of the topic. Thank You

 

[161927]

You could reason that because increasing the frequency of a wave increases it's energy that increasing the frequency increases the intensity. The intensity of an electromagnetic wave is given by

We can say that increasing the frequency may increase the intensity, but we cannot say increasing the intensity will always increase the frequency.

 

[physics junkie]

Do not assume because I ask such broad questions I am ignorant of the topic. Thank You

My bad. Thought you were hoping everyone would do the leg work for you. Do you remember what the question was?

 

[unsung]

I was wondering is there any relation to waves, frequency, and intensity. If you increase the frequency of a wave does that increase the intensity of the wave? What is the relation between wavelength and intensity. Also how do these concepts apply to particles. Is the relation E=(frequency)(wavelength) for particles, correct?

Just want to add one thing here... don't know how helpful this will be, but when you mentioned intensity/freq, what immediately came to mind was the photoelectric effect.

For the photoelectric effect, the KE of the ejected electron is dependent solely on the *frequency* of the incident radiation. But, the # of electrons ejected has to do with both the frequency and the *intensity* of the incident light. Specifically, higher intensity radiation will kick off more electrons. But the KE each of those electrons has has to do with the frequency of the radiation, not the intensity.

There's a cutoff frequency below which, light will not eject any electrons from the metal. This is why red light (low freq) of any intensity will not eject any electrons-- it doesn't have enough energy (as dictated by its freq). But past that cutoff frequency, the # of electrons that get ejected has to do with the light's intensity. Anyway, I think it's more helpful to understand the distinctions between concepts like that in terms of physical phenomena, instead of just thinking about them in terms of equations...

I think of intensity as like "brightness" (for light) or "volume" (for sound). Frequency for light is color, if we're talking visible spectrum, or different types of radiation (IR vs. x-ray), if we're talking about the whole spectrum. Frequency for sound is like pitch. So, if you think about it that way, it's clear that "brightness" and color are really distinct concepts, for intensity and frequency are really distinct concepts too. Somebody correct me if I'm wrong.

 

[Zerconia2921]

I was wondering is there any relation to waves, frequency, and intensity. If you increase the frequency of a wave does that increase the intensity of the wave? What is the relation between wavelength and intensity. Also how do these concepts apply to particles. Is the relation E=(frequency)(wavelength) for particles, correct?

E= hf where E is energy, h is Plank's constant and f is frequency. This can also be written as E = hc/wave length where c is speed of light.

If you look at this equation you will answer your own question. As you increase {f} your increasing energy a direct relation.

If you increase wave length your fraction gets smaller therefore less energy.
hope this helped.

As for particles i would think of them riding on the wave. Those particles that are closer to gether would have a shorter wave therefore higher frequency wheres particles father away will have a longer wave length and therefore less engery.