| Topic: |
Science > Physics |
| User: |
"John Doe" |
| Date: |
07 Apr 2006 12:03:38 PM |
| Object: |
internal energy, kinetic theory, kinetic energy |
I think
#1) according to the Bohr model the internal eneregy of a hydrogen atom is
restricted to certain discrete values (i.e. n = 1, 2, 3, 4, ....)
#2) accoding to the kinetic theory of gases, molecular speeds are
distributed over a wide range with a mean value that depends on the
temperature of the gas (KE = 3/2KT where T is absolute temperature in
kelvin. I am guessing the formula is 3/2KT)
#3) Maximum kinetic energy of a photoelectron ejected from a metal plate is
linearly (with a positive slope) related to the frequency of the light
incident on the plate because KE = h * f - w where h is the plank's
constant, f = frequency and W = work function.
Am I right?
about #3, does it make sense to have a negative maximum kinetic energy?
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| User: "James Copeland" |
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| Title: Re: internal energy, kinetic theory, kinetic energy |
07 Apr 2006 04:34:09 PM |
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"John Doe" <johndoe@nothing.edu> wrote in message
news:KXwZf.1214$BS2.566@newsread1.news.pas.earthlink.net...
I think
#1) according to the Bohr model the internal eneregy of a hydrogen atom is
restricted to certain discrete values (i.e. n = 1, 2, 3, 4, ....)
#2) accoding to the kinetic theory of gases, molecular speeds are
distributed over a wide range with a mean value that depends on the
temperature of the gas (KE = 3/2KT where T is absolute temperature in
kelvin. I am guessing the formula is 3/2KT)
#3) Maximum kinetic energy of a photoelectron ejected from a metal plate
is linearly (with a positive slope) related to the frequency of the light
incident on the plate because KE = h * f - w where h is the plank's
constant, f = frequency and W = work function.
Am I right?
about #3, does it make sense to have a negative maximum kinetic energy?
In #2, KE = (3/2)kT. (The way you wrote it implies division of 3 by the
product 2kT.) Btw, Boltzmann's constant is small k, not K.
In #3, the maximum kinetic energy of an "ejected" photoelectron will
certainly be positive and never negative. KE(max) = h*f - w, as you have
stated. h*f is the (positive) energy of a light photon, and w is the
(positive) work function, as you said. w is the energy used up in just
getting the electron out of the metal with no leftover energy to appear as
kinetic energy of the electron. So h*f - w represents any energy left over
after getting that electron out of the metal and appears as electron's
knietic energy. (Conceptually,if photon energy, h*f, just equals w, then the
electron will just be barely pulled out of the metal and left at rest
outside the metal. If h*f is less than w, then of course the photon is not
energetic enough to even free the electron from the metal.)
JimC
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| User: "Old Man" |
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| Title: Re: internal energy, kinetic theory, kinetic energy |
07 Apr 2006 03:37:18 PM |
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"John Doe" <johndoe@nothing.edu> wrote in message
news:KXwZf.1214$BS2.566@newsread1.news.pas.earthlink.net...
I think
#1) according to the Bohr model the internal eneregy of a hydrogen atom is
restricted to certain discrete values (i.e. n = 1, 2, 3, 4, ....)
#2) accoding to the kinetic theory of gases, molecular speeds are
distributed over a wide range with a mean value that depends on the
temperature of the gas (KE = 3/2KT where T is absolute temperature in
kelvin. I am guessing the formula is 3/2KT)
#3) Maximum kinetic energy of a photoelectron ejected from a metal plate
is linearly (with a positive slope) related to the frequency of the light
incident on the plate because KE = h * f - w where h is the plank's
constant, f = frequency and W = work function.
Am I right?
about #3, does it make sense to have a negative maximum kinetic energy?
Sure. Negative KE_max means that no electrons are emitted.
[Old Man]
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