## HW 1.41 Help with understanding final answer

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

Alexander Hari 1L
Posts: 30
Joined: Wed Feb 14, 2018 3:02 am

### HW 1.41 Help with understanding final answer

I calculated the velocity of question 41: "What is the velocity of a neutron of wavelength 100. pm"
I used the equation v=(h x lambda)/mass of a neutron and got 3.96 x 10^-24m, but the answer in the back of the book says 3.96 x 10^3m. How is this the answer? What did I do incorrectly? Thanks!

Chem_Mod
Posts: 18150
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 423 times

### Re: HW 1.41 Help with understanding final answer

The problem you made was with converting the de Broglie wavelength equation to calculate velocity. In your answer you said $v=(h* \lambda )/m_{neutron}$ but when you convert the equation $\lambda = h/(m*v)$ to solve for v you should multiply both sides of the equation by v then divide both sides by $\lambda$
to get that $v=h/(m_{neutron}*\lambda )$. If you plug in the values for h, mneutron, and $\lambda$ you should get the answer of 3.96 x 103.