## Example from Friday's Lecture (10/12/18)

$c=\lambda v$

905085650
Posts: 62
Joined: Fri Sep 28, 2018 12:19 am

### Example from Friday's Lecture (10/12/18)

Hi,

On Friday we went over a problem at the end of class that asked if the wavelength of an electron traveling at 5.3 x 10^6 m/s could be calculated. When we plugged in the numbers, we were given 9.11 x 10^-31 kg. Where does this number come from?

Thank you!!

Jonathan Cheng 3C
Posts: 30
Joined: Fri Sep 28, 2018 12:23 am
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### Re: Example from Friday's Lecture (10/12/18)

9.11 * 10^-31 kg is the weight of an electron. This value is given

becca_vandyke_4b
Posts: 30
Joined: Fri Sep 28, 2018 12:29 am

### Re: Example from Friday's Lecture (10/12/18)

You use the mass of the electron when calculating the momentum (p) in the problem. I believe the example he gave us listed the velocity of the electron but not the mass of it. So to calculate p=(m)(v) he plugged in the mass which I guess is considered a constant.

Mhun-Jeong Isaac Lee 1B
Posts: 54
Joined: Fri Sep 28, 2018 12:17 am

### Re: Example from Friday's Lecture (10/12/18)

Yes, Lavelle said that the mass is given. So it is safe to assume that the mass will be on the constants sheet for any tests/exams.