## 1.37 [ENDORSED]

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

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edenzeboulon3A
Posts: 4
Joined: Fri Sep 29, 2017 7:07 am

### 1.37

Hi!
Can someone please explain 1.37 from the textbook HW problems. I know I need to use the De Broglie equation, but how do I find the mass of a proton/neutron? Is it just a value I should have memorized, or would it be given?

1.37) Protons and neutrons have nearly the same mass. How different are their wavelengths? Calculate the the wavelength of each particle when traveling at 2.75 x 10^5 m/s in a particle accelerator and report the difference as a percentage of the wavelength of a neutron.

Thanks so much!

veneziaramirez 3I
Posts: 57
Joined: Fri Sep 29, 2017 7:07 am

### Re: 1.37  [ENDORSED]

I think the mass would be given since in Example 1.6, Self-Test 1.6A, the question mentions that the mass of an electron can be found inside the back cover of the book. There, you can also find the mass of a proton.

Danah Albaaj 1I
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

### Re: 1.37

You can also find the masses of both particles on the class website! It's in a worksheet named constants and equations, just in case you wanna have a separate page to look at so you're not constantly flipping the pages of your book :)

Alissa Stanley 3G
Posts: 22
Joined: Fri Sep 29, 2017 7:06 am
Been upvoted: 1 time

### Re: 1.37

On #37 and #41, you need to know the mass of a proton and neutron, which are not given in the question. Is this something we should memorize for tests? Are there any other masses that we should memorize the value of?

Golbarg Rahimi 3k
Posts: 26
Joined: Sat Jul 22, 2017 3:01 am

### Re: 1.37

Hi
I think their masses would be given on a separate sheet attached to the exam paper.

Jana Sun 1I
Posts: 52
Joined: Sat Jul 22, 2017 3:00 am

### Re: 1.37

I can confirm that a constants and equations sheet will be provided! Going back to the original question though, I was confused by the last part: "report the difference as a percentage of the wavelength of a neutron". Are we supposed to just calculate both wavelengths, find the difference then divide by the wavelength of a neutron? Wouldn't we just get 0% since the wavelengths end up being nearly identical?

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