PChem322 s22 w1 - Revision history

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Announcements

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Thurs, Jan 13, 2022

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← Older revision		Revision as of 15:22, 14 January 2022
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−	:2)	+	:2)Sec 1.4 The Photoelectric Effect
		+	:Please read this section. The quick and dirty explanation of the photoelectric effect (PE) is this...when you shine light, with high enough energy, onto a metal surface you knock off electrons (theses are referred to as photoelectrons, although they are no different from any other electron). These electrons leave the surface with a certain velocity. It turns out that the energy of the light (''hν'')= the energy which holds the electron on the surface (i.e., the work function, ''φ'') + the kinetic energy of moving electron (1/2mv<sup>2</sup>, where v is velocity). This figure 1.4 below shows that as the energy of light (plotted as the frequency on the x-axis) vs the kinetic energy of the photoelectron (y-axis) yields a straight line with a slope equal to Plank's Constant! Here is a totally separate experiment (from BBR) that requires the exactly same constant of 6.626e-34 Js.
		+	:[[File:Screen Shot 2021-01-29 at 9.51.50 AM.png\|300px]]
		+
		+	:Study example problem 1.1 to help you complete the [[Media:HW1_Photoelectric.pdf\|Photoelectric Effect worksheet]].
		+
		+	''Have a great weekend...be safe...be smart...relax.''
		+
		+	END

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 ====Class Assignment====
-:1) I am excited to hear that all of you were successful in completing the Excel Challenge i gave you in lab yesterday dealing with reproducing Figure 1.2, the Blackbody Radiation problem (Sec 1.3). Although it is not necessary to fully understand the concepts of blackbody radiation (BBR) in order to complete the Excel graphing, you may have looked over section 1.3...or not.
+:1) I am excited to hear that all of you were successful in completing the Excel Challenge i gave you in lab yesterday dealing with reproducing Figure 1.2, the Blackbody Radiation problem (Sec 1.3)...otherwise i would have heard from you. Although it is not necessary to fully understand the concepts of blackbody radiation (BBR) in order to complete the Excel graphing, you may have looked over section 1.3...or not. Let's do this now...
 :BBR is fairly simple, hot (any temp over absolute 0) objects emits (or radiates) electromagnetic radiation (light). How do we know this? We built sophisticated scientific equipment in order to measure the properties of the emitted light...frequency (&nu;) and intensity. Figure 1.2 (page 21 and above) shows that an object at 6000 K has a &nu;<sub>max</sub> of ~3.5e14 Hz...meaning the frequency of the maximum intensity of light emitted (''&nu;<sub>max</sub>'') is 3.5e14 Hz. If the temperature of the object is lowered to 5000 K, then the ''&nu;<sub>max</sub>'' = 2.8e14 Hz...and so on. The ''&nu;<sub>max</sub>'' is dependent on the temperature.
-:The equation i used to reproduce this figure in Excel is eq. 1.7. Eq 1.7 is presented as a differential equation, ie contains a variable of differentiation, ''d&nu;''...i simply removed the ''d&nu;'' and treated the ''&nu;'' as the x-value and the spectral density (''&rho;'') as the y-value.
+:The equation i used to reproduce this figure in Excel is eq. 1.7. Eq 1.7 is presented as a differential equation, ie contains a variable of differentiation, ''d&nu;''...i simply removed the ''d&nu;'' and treated the ''&nu;'' as the x-value and the spectral density (''&rho;'') as the y-value. As you will read, when classical mechanics was applied to the problem of BBR this "math" predicted that all objects would radiate light in the ultraviolet and above regions, which would be catastrophic...we would all be dead...hence the ''ultraviolet catastrophe.'' As stated in the reading, it was Max Plank who figured out the math...which required him to treat the energy of the "oscillators" as if they had only discrete energies and not continuous as classical mechanic predicted. The constant now called, Plank's constant was required in his derivation.

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 :1) I am excited to hear that all of you were successful in completing the Excel Challenge i gave you in lab yesterday dealing with reproducing Figure 1.2, the Blackbody Radiation problem (Sec 1.3). Although it is not necessary to fully understand the concepts of blackbody radiation (BBR) in order to complete the Excel graphing, you may have looked over section 1.3...or not.
-:BBR is fairly simple, hot (any temp over absolute 0) objects emits (or radiates) electromagnetic radiation (light). How do we know this? We built sophisticated scientific equipment in order to measure the properties of the emitted light...frequency (&nu;) and intensity. Figure 1.2 (page 21 and above) shows that an object at 6000 K has a &nu;<sub>max</sub> of ~3.5e14 Hz...meaning the frequency of the maximum intensity of light emitted (&nu;<sub>max</sub>) is 3.5e14 Hz. If the temperature of the object is lowered to 5000 K, then the &nu;<sub>max</sub> = 2.8e14 Hz...and so on. The &nu;<sub>max</sub> is dependent on the temperature.
+:BBR is fairly simple, hot (any temp over absolute 0) objects emits (or radiates) electromagnetic radiation (light). How do we know this? We built sophisticated scientific equipment in order to measure the properties of the emitted light...frequency (&nu;) and intensity. Figure 1.2 (page 21 and above) shows that an object at 6000 K has a &nu;<sub>max</sub> of ~3.5e14 Hz...meaning the frequency of the maximum intensity of light emitted (''&nu;<sub>max</sub>'') is 3.5e14 Hz. If the temperature of the object is lowered to 5000 K, then the ''&nu;<sub>max</sub>'' = 2.8e14 Hz...and so on. The ''&nu;<sub>max</sub>'' is dependent on the temperature.
-:The equation i used to reproduce this figure in Excel is eq. 1.7. Eq 1.7 is presented as a differential equation, ie contains a variable of differentiation, ''d&nu;''...i simply removed the ''d&nu;'' and treated the &nu; as the x-value and the spectral density (&rho;) as the y-value.
+:The equation i used to reproduce this figure in Excel is eq. 1.7. Eq 1.7 is presented as a differential equation, ie contains a variable of differentiation, ''d&nu;''...i simply removed the ''d&nu;'' and treated the ''&nu;'' as the x-value and the spectral density (''&rho;'') as the y-value.

← Older revision		Revision as of 14:49, 14 January 2022
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	====Class Assignment====		====Class Assignment====
−	:1) I am excited to hear that all of you were successful in completing the Excel Challenge i gave you in lab yesterday dealing with the Blackbody Radiation problem (Sec 1.3)	+	:1) I am excited to hear that all of you were successful in completing the Excel Challenge i gave you in lab yesterday dealing with reproducing Figure 1.2, the Blackbody Radiation problem (Sec 1.3). Although it is not necessary to fully understand the concepts of blackbody radiation (BBR) in order to complete the Excel graphing, you may have looked over section 1.3...or not.
		+
		+	:BBR is fairly simple, hot (any temp over absolute 0) objects emits (or radiates) electromagnetic radiation (light). How do we know this? We built sophisticated scientific equipment in order to measure the properties of the emitted light...frequency (ν) and intensity. Figure 1.2 (page 21 and above) shows that an object at 6000 K has a ν<sub>max</sub> of ~3.5e14 Hz...meaning the frequency of the maximum intensity of light emitted (ν<sub>max</sub>) is 3.5e14 Hz. If the temperature of the object is lowered to 5000 K, then the ν<sub>max</sub> = 2.8e14 Hz...and so on. The ν<sub>max</sub> is dependent on the temperature.
		+
		+	:The equation i used to reproduce this figure in Excel is eq. 1.7. Eq 1.7 is presented as a differential equation, ie contains a variable of differentiation, ''dν''...i simply removed the ''dν'' and treated the ν as the x-value and the spectral density (ρ) as the y-value.

← Older revision		Revision as of 14:34, 14 January 2022
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	====Class Assignment====		====Class Assignment====
		+	:1) I am excited to hear that all of you were successful in completing the Excel Challenge i gave you in lab yesterday dealing with the Blackbody Radiation problem (Sec 1.3)

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 :1) Well it was not a full first week, but we have made it! Congrats.
 :2) As a reminder, we will meet next week in-person for lab on Thurs. There are only 6 of us in the class so we can distance easily in CSB 373. Bring your laptop or you can use one of the desktop computers in this space.
-:3) The NOVA program never gets old. There was a statement made in the program stating..."I am foot soldier of science." As you think about the early days of the development of scientific principles there are certainly key historical players (now written down in your lab notebooks), but let's not forget all the others who work behind the scenes (the foot soldiers) making thermometers, preparing samples, etc, without them science would progress at a snails pace. Although it may be a bit too earlier for you to contemplate your role in science, but you too are a foot soldier. You represent a critical part of the scientific ecosystem. Some of you will go on to be the Antoine Lavoisier of your time, but most of us will continue to be foot soldiers for science and as you might expect, the scientific ecosystem needs lot os foot soldiers! Keep up the good work. If this topic resonates with you, consider having a look at this paper titled, [[Media:FootSoldier.pdf|The foot soldiers of science.]]
+:3) At this point, you should have Igor and Mathematica loaded onto your laptop. If this is not the case, you have more homework than i assigned. If you are having any issues please let me know and we can either get together and work this out or do it via email/phone. We will use both software packages in lab next week.
 ====Class Assignment====

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	:[[File:Screen Shot 2021-01-27 at 9.18.22 AM.png\|300px]]		:[[File:Screen Shot 2021-01-27 at 9.18.22 AM.png\|300px]]
	:We will discuss more about blackbody radiation in lecture tomorrow. For now, please download the Excel file and add the other data to the Excel graph. I am in my office until ~5pm, if you need any help.		:We will discuss more about blackbody radiation in lecture tomorrow. For now, please download the Excel file and add the other data to the Excel graph. I am in my office until ~5pm, if you need any help.
		+
		+	===Friday, Jan 14, 2022===
		+	====Announcements====
		+	:1) Well it was not a full first week, but we have made it! Congrats.
		+	:2) As a reminder, we will meet next week in-person for lab on Thurs. There are only 6 of us in the class so we can distance easily in CSB 373. Bring your laptop or you can use one of the desktop computers in this space.
		+	:3) The NOVA program never gets old. There was a statement made in the program stating..."I am foot soldier of science." As you think about the early days of the development of scientific principles there are certainly key historical players (now written down in your lab notebooks), but let's not forget all the others who work behind the scenes (the foot soldiers) making thermometers, preparing samples, etc, without them science would progress at a snails pace. Although it may be a bit too earlier for you to contemplate your role in science, but you too are a foot soldier. You represent a critical part of the scientific ecosystem. Some of you will go on to be the Antoine Lavoisier of your time, but most of us will continue to be foot soldiers for science and as you might expect, the scientific ecosystem needs lot os foot soldiers! Keep up the good work. If this topic resonates with you, consider having a look at this paper titled, [[Media:FootSoldier.pdf\|The foot soldiers of science.]]
		+
		+	====Class Assignment====

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 :::2) Use the summary at the end of the program to draw out a temperature timeline...and add the points where O<sub>2</sub>(g), N<sub>2</sub>(g), H<sub>2</sub>(g), and He(g) liquify.
-:3) Challenge: Attached [[file:Blackbody_excel.xlsx|here]] is an Excel file that reproduces part of figure 1.2 (Blackbody Radiation).
+:3) Challenge: Attached [[Media:Blackbody_excel.xlsx|here]] is an Excel file that reproduces part of figure 1.2 (Blackbody Radiation).
 :[[File:Screen Shot 2021-01-27 at 9.18.22 AM.png|300px]]
 :We will discuss more about blackbody radiation in lecture tomorrow. For now, please download the Excel file and add the other data to the Excel graph. I am in my office until ~5pm, if you need any help.