## Class Lecture Work Example Question [ENDORSED]

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

204580382
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### Class Lecture Work Example Question

During lecture when Dr. Lavelle walked us through the worked examples using De Broglie's Equation I was a bit confused on the second work example when calculating the wavelength of an electron traveling at 5.3 *10^6 ms^-1.

I need clarification on why we used 9.11*10^-1 kg for the mass and how we got that number.

Thanks!

Joe Rich 1D
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### Re: Class Lecture Work Example Question  [ENDORSED]

De Broglie's Equation is λ=h/p, where p=mass x velocity. To calculate the wavelength of an electron, we can plug in the (given) velocity of the electron and the mass of an electron into De Broglie's Equation. The mass of an electron is a constant (9.11E-31 kg). We want the mass in kg because h is given in J/s, and J=kgm^2/s^2.

Johana Jeon 1A
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Joined: Sun Feb 12, 2017 3:00 am

### Re: Class Lecture Work Example Question

During his office hour, Dr. Lavelle said mass of electron is always (9.10938 x 10^-31 kg) and this formula will be given in the tests
On the first problem, we used 1.50 x 10^3 kg as our mass because it is given in the problem
Lastly, we want SI units in m because SI unit for Joules is: kg * m^2 * s^-2 and therefore, kg, m, s cancel