Module 7 Question's (1 Viewer)

[kkk579]

1) What is the relationship between Plancks eqn, E=hf, and the Blackbody radiation graph.

2) What previous postulates/laws resulted in classical physics predicting the Uv catastrophe graph.

3) For the Hertz experiment, why were there no sparks at the nodes? How were these sparks even generated? Is it because of the extremely high voltage jumping from one end of the ring to the next end.

 

[kkk579]

Bump smo pls help

 

[kkk579]

bump

 

[wizzkids]

1) What is the relationship between Planck's eqn, E=hf, and the Blackbody radiation graph.

Ans:
The short answer to your question is, "There is no relationship".
The Planck equation does not determine the Blackbody radiation graph. Rather it works the other way around.
The shape of the blackbody radiation graph determines what the Planck equation must do in order for it to agree with the evidence.

The blackbody radiation graph is empirically derived, it is a result of measurement. For twenty years nobody could explain the shape of the blackbody radiation graph. In 1902 Max Planck, in an act of scientific desperation, proposed that maybe Nature has decided that radiation energy cannot be emitted in any arbitrary amount. Maybe radiant energy is emitted in packets, and the quantity of energy in each packet is proportional to the frequency of the radiation.
Using this hypothesis, and a new mathematical model, all that Planck had to do was find the proportionality constant between E the quantum of energy, and f the frequency of the radiation. This he did by adjusting the value of h until the equation fitted the empirical curve. The value obtained for h in this way was very, very small, about 6 x 10^-34 J.s

 

[kkk579]

Ans:
The short answer to your question is, "There is no relationship".
The Planck equation does not determine the Blackbody radiation graph. Rather it works the other way around.
The shape of the blackbody radiation graph determines what the Planck equation must do in order for it to agree with the evidence.

The blackbody radiation graph is empirically derived, it is a result of measurement. For twenty years nobody could explain the shape of the blackbody radiation graph. In 1902 Max Planck, in an act of scientific desperation, proposed that maybe Nature has decided that radiation energy cannot be emitted in any arbitrary amount. Maybe radiant energy is emitted in packets, and the quantity of energy in each packet is proportional to the frequency of the radiation.
Using this hypothesis, and a new mathematical model, all that Planck had to do was find the proportionality constant between E the quantum of energy, and f the frequency of the radiation. This he did by adjusting the value of h until the equation fitted the empirical curve. The value obtained for h by in this way was very small, about 6 x 10^-34 J.s

Tysm for this answer, do you mind also answering this:
1) Why did classical physics believe that intensity of light shone upon a metal surface was what affected the max ke of electrons rather than frequency
2) why do only accelerating charges produce emr?

 

[wizzkids]

3) For the Hertz experiment, why were there no sparks at the nodes? How were these sparks even generated? Is it because of the extremely high voltage jumping from one end of the ring to the next end.

Ans:
I'm guessing that you are referring to Hertz's experiment in the year 1886 into the generation and detection of electromagnetic waves.
Sparks were detected by Hertz in the loop detector. The spark gap had to be adjusted to a fraction of 1 millimetre, and the induced potential difference at the gap must have been about 200 volts, enough to jump a gap of about 0.25 millimetres. The sparks were generated when the e-m waves passed through the centre of the loop. The changing electric and magnetic flux in the wave accelerated the charged particles (electrons) in the conducting loop.
No sparks were generated when the plane of the loop was perpendicular to the axis of the transmitter (see the figure below).
The loop was made of a good conductor and so there would be virtually no electrical resistance around the loop; the 200V potential difference would appear at the air gap.

 

[wizzkids]

2) What previous postulates/laws resulted in classical physics predicting the UV catastrophe graph.

Ans:
The previous best theory for the blackbody radiation spectrum was called the Rayleigh-Jeans Law, after the two scientists who developed it.
I recommend you watch this video clip which will answer your question much better that I can summarise.