## Post module #38

$\lambda=\frac{h}{p}$

kateraelDis1L
Posts: 104
Joined: Wed Sep 30, 2020 9:54 pm

### Post module #38

At what velocity is an electron moving if it has a de Broglie wavelength of 7.0 × 10-11 m?

I understand that I can solve for velocity with the equation v=h/m(lambda). But can't grasp this question.

Helena Xu 1I
Posts: 53
Joined: Wed Sep 30, 2020 9:51 pm
Been upvoted: 1 time

### Re: Post module #38

You would plug in the numbers for h, m, and lambda, into that equation v=h/m(lambda). h is Planck's constant, which is 6.626 x 10^-34 Js. The mass of the electron is m, which is 9.11 x 10^-31 kg, and the symbol lambda is the wavelength, given to you in the question (7.0 x 10^-11 m). When you plug these numbers in the equation and solve, you would get the velocity. I hope this helps!

Immi Lee - 1D
Posts: 98
Joined: Wed Sep 30, 2020 9:58 pm

### Re: Post module #38

^ If anyone is wondering how he got the mass of the electron it is another constant: 9.11 x 10^-31 kg.

rhettfarmer-3H
Posts: 101
Joined: Wed Sep 30, 2020 9:59 pm

### Re: Post module #38

Hey, I like this problem. Quite simple as we get use to the equation. however, I agree to do this problem you must understand the constant of electron which is 9.11X10^-31 Kg. Furthermore, the equation goes as p=h/lamanda. We are luckily given the wave length which makes it easy since everything else is constants/given.
So plug lamanda in and planks constant and divert p into MV and solve. SHOWN IN WORK>
Attachments
IMG_2779.pdf