Intensity / Frequency

[letaps]

Hey,

What is the relationship between intensity and freqency?

Thanks

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[engineeredout]

Intensity is directly proportional to the square of frequency (double frequency = 4X intensity)

 

[domani]

Intensity is directly proportional to the square of frequency (double frequency = 4X intensity)

how could you relate frequency and intensity? i think you're thinking of amplitude and intensity...

 

[engineeredout]

how could you relate frequency and intensity? i think you're thinking of amplitude and intensity...

If you actually look up the formula for intensity (which even the OP should be able to do),

I = 1/2*p*w^2*A^2*v

p = density
A = amplitude
v = velocity
w = angular frequency = 2*pi*f.

I win.

 

[domani]

lol. do you think that works for light waves? explain

 

[futuredoctor10]

I = 1/2*p*w^2*A^2*v

Do we have to know this equation for the MCAT? Just checking

This probably comes into the MCAT in terms of the photoelectric effect. Increasing the intensity of light increases the number of photons in the light beam, thus increasing the number of electrons ejected from a metal (without increasing the energy that each electron possesses)

 

[engineeredout]

Wait, the OP is talking about sound intensity right...?

 

[domani]

so, i emailed my physics prof about that equation and he said it is isolated only to resonating systems or systems like a mass spring pendulum that have dampening (basically any system where an external force might be present). furthermore, he exclaimed that intensity and frequency are different parameters completely and CANNOT be used to define one another in a natural wave system.

 

[futuredoctor10]

Wait, the OP is talking about sound intensity right...?

Oops yeah you are right... I was going on about LIGHT intensity/frequency's relationship hehe.

 

[friyaz]

Do we have to know this equation for the MCAT? Just checking

This probably comes into the MCAT in terms of the photoelectric effect. Increasing the intensity of light increases the number of photons in the light beam, thus increasing the number of electrons ejected from a metal (without increasing the energy that each electron possesses)

i believe this is backwards... photoelectric effect says increasing number of photons doesn't cause electrons to be emitted- and assuming quantum theory (quantization of energy), this is proof for the particle nature of light, in that more particles cannot make electrons eject, since there would have to be a 1 on 1 collision.

instead, increasing the energy of the light by increasing the frequency did, in fact, affect the electrons.

oui ou non?

 

[JasonE]

according to examkrackers physics, intensity is proportional to both the square of the amplitude and sqaure of the frequency for all waves.

 

[futuredoctor10]

Friyaz, I think that when metal absorbs photons higher than the threshhold frequency, the electrons are emitted in a 1:1 ratio in relation to the incoming photons.

You are right that increasing the energy of the photons will affect the electrons (it increases KE of the emitted electrons). But, I still think that a photon above the threshold frequency has energy to eject a single electron.

 

[futuredoctor10]

intensity is proportional to both the square of the amplitude and sqaure of the frequency for all waves.

JasonE - so Intensity is proportional to A^2 and f^2 for light AND sound waves? that's a good fact to know I'd imagine. Thanks for clarifying with EK Physics.

What do you think about our related, somewhat off-topic discussion of photoelectric effect? Just trying to verify what is true/false about our (friyaz/my) posts above.

 

[futuredoctor10]

I don't think light of higher intensity necessitates light of higher frequency?

I did some research and apparently light of HIGHER Intensity means you have MORE light (but of the same frequency).

 

[AZFutureDoc]

This doesn't work with light. But yes, there IS the equation previously mentioned.

I'm not sure why anyone is questing this, as long as we're not all deaf and we have listened to music before. What makes you turn down the volume when it is uncomfortably loud? Its not the bass, its high pitched notes. You double the frequency, you quadruple the intensity.

C'mon guys, this is not talking quantum physics. This is opening music and listening to iTunes, an act that I'm sure some of you are probably doing right now.