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### Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 7:49 pm
I’m having some trouble with all the equations that we’ve learned so far. Can someone list them and explain when we’re supposed to use each one?

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 7:54 pm
Is there a specific example or equation you're having trouble with? I'm not sure if I can describe all of them.

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 8:13 pm
Ryan Chew 1C wrote:Is there a specific example or equation you're having trouble with? I'm not sure if I can describe all of them.

Maybe for problem 1a.15 I’m confused about the Rydberg equation.

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 8:14 pm
Hi Ellis! This is Ariel.

Here's a general list from my notes:

c = λ ν
-- Used to calculate wavelength/frequency

E(photon) = h ν
-- Used to calculate energy per single photon
-- Bohr Frequency Condition: v = ∆E/h; used to calculate frequency

E(photon) = Work Function/Threshold Energy + EK
EK =(1/2)mv^2
-- Used for Photoelectric Effect problems (when an electron is ejected)

En = -(h)(R)/n^2 for n =1,2...
-- Used for electron transitions for the H-atom spectrum

λ = h/p, where p = mass x velocity; λ = h/(mass x velocity)
-- De Broglie Equation: Used to find wavelength/"wavelike properties" of moving objects (only noticeable for objects with extremely small mass)

There is also the Heisenberg Indeterminacy Equation (∆p ∆x ≥ h/4π) and Schrodinger's Equation (Hψ = Eψ), but we haven't covered those yet! Hope this helps! Also, there is a list of constants and equations on the Chem 14A page, and it has helped me keep track of all of these! Let me know if there is a mistake here or if there is an easier way to list these!

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 8:17 pm
Ariel Fern 3A wrote:Hi Ellis! This is Ariel.

Here's a general list from my notes:

c = λ ν
-- Used to calculate wavelength/frequency

E(photon) = h ν
-- Used to calculate energy per single photon
-- Bohr Frequency Condition: v = ∆E/h; used to calculate frequency

E(photon) = Work Function/Threshold Energy + EK
EK =(1/2)mv^2
-- Used for Photoelectric Effect problems (when an electron is ejected)

En = -(h)(R)/n^2 for n =1,2...
-- Used for electron transitions for the H-atom spectrum

λ = h/p, where p = mass x velocity; λ = h/(mass x velocity)
-- De Broglie Equation: Used to find wavelength/"wavelike properties" of moving objects (only noticeable for objects with extremely small mass)

There is also the Heisenberg Indeterminacy Equation (∆p ∆x ≥ h/4π) and Schrodinger's Equation (Hψ = Eψ), but we haven't covered those yet! Hope this helps! Also, there is a list of constants and equations on the Chem 14A page, and it has helped me keep track of all of these! Let me know if there is a mistake here or if there is an easier way to list these!

Haha thanks Ariel! I really appreciate it this is super helpful :)

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 8:25 pm
It's important to distinguish between equations that are relevant to light (EM radiation) and quantum movement of electrons. For light specifically, you should pay attention to:
These two equations are applied to light in the theory that light is a wave:
c = λv = 3*10^8 (speed of light = wavelength * frequency)
E=hv (Energy = Planck's constant * frequency)
h = 6.63 * 10^-34 (Planck's constant)
These two equations are applied to light in the theory that light is a particle (photon):
E (energy of photon) - Work Function (energy to remove electron from a metal) = Kinetic Energy
When a photon hits a metal surface, it can remove electrons from that metal. The energy of the photon moves to the electron, causing the electron to move.
E = (-hR)/n^2
n = energy level
R = Rydberg Constant = 3.29 * 10^15

Remember, De Brogile Equation is for electrons only. Do not use this equation with light!

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 8:26 pm
It's important to distinguish between equations that are relevant to light (EM radiation) and quantum movement of electrons. For light specifically, you should pay attention to:
These two equations are applied to light in the theory that light is a wave:
c = λv = 3*10^8 (speed of light = wavelength * frequency)
E=hv (Energy = Planck's constant * frequency)
h = 6.63 * 10^-34 (Planck's constant)
These two equations are applied to light in the theory that light is a particle (photon):
E (energy of photon) - Work Function (energy to remove electron from a metal) = Kinetic Energy
When a photon hits a metal surface, it can remove electrons from that metal. The energy of the photon moves to the electron, causing the electron to move.
E = (-hR)/n^2
n = energy level
R = Rydberg Constant = 3.29 * 10^15

Remember, De Brogile Equation is for electrons only. Do not use this equation with light!

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 9:16 pm
Natalie Wang 1B wrote:It's important to distinguish between equations that are relevant to light (EM radiation) and quantum movement of electrons. For light specifically, you should pay attention to:
These two equations are applied to light in the theory that light is a wave:
c = λv = 3*10^8 (speed of light = wavelength * frequency)
E=hv (Energy = Planck's constant * frequency)
h = 6.63 * 10^-34 (Planck's constant)
These two equations are applied to light in the theory that light is a particle (photon):
E (energy of photon) - Work Function (energy to remove electron from a metal) = Kinetic Energy
When a photon hits a metal surface, it can remove electrons from that metal. The energy of the photon moves to the electron, causing the electron to move.
E = (-hR)/n^2
n = energy level
R = Rydberg Constant = 3.29 * 10^15

Remember, De Brogile Equation is for electrons only. Do not use this equation with light!

Hey Natalie! That's definitely a great strategy to use: thinking in terms of light VS. electrons. So far I have just been figuring out equations based on variables and what is given, but having another technique to consider is awesome as well! Thanks for sharing!

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 9:17 pm
Ariel Fern 3A wrote:Hi Ellis! This is Ariel.

Here's a general list from my notes:

c = λ ν
-- Used to calculate wavelength/frequency

E(photon) = h ν
-- Used to calculate energy per single photon
-- Bohr Frequency Condition: v = ∆E/h; used to calculate frequency

E(photon) = Work Function/Threshold Energy + EK
EK =(1/2)mv^2
-- Used for Photoelectric Effect problems (when an electron is ejected)

En = -(h)(R)/n^2 for n =1,2...
-- Used for electron transitions for the H-atom spectrum

λ = h/p, where p = mass x velocity; λ = h/(mass x velocity)
-- De Broglie Equation: Used to find wavelength/"wavelike properties" of moving objects (only noticeable for objects with extremely small mass)

There is also the Heisenberg Indeterminacy Equation (∆p ∆x ≥ h/4π) and Schrodinger's Equation (Hψ = Eψ), but we haven't covered those yet! Hope this helps! Also, there is a list of constants and equations on the Chem 14A page, and it has helped me keep track of all of these! Let me know if there is a mistake here or if there is an easier way to list these!

This is so helpful, thank you!

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 10:55 pm
Anyone have any tips for distinguishing between formulas designated for electrons vs those related to light? I'm having trouble keeping all their meanings and uses straight.

### Re: Equations We’ve Learned So Far

Posted: Sat Oct 12, 2019 10:58 pm
A good rule of thumb is that any equation with mass (m) as one of the variables CANNOT be used for light, as light particles (aka photons) have no mass!

### Re: Equations We’ve Learned So Far

Posted: Sun Oct 13, 2019 12:08 am
The responses to this post are really helpful. I was looking at my notes but they were somewhat disorganized. This is what I needed for understanding the recent equations from the lectures, so thank you.