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### Class Lecture Work Example Question

Posted: **Sun Jul 02, 2017 3:50 pm**

by **204580382**

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!

### Re: Class Lecture Work Example Question [ENDORSED]

Posted: **Sun Jul 02, 2017 3:55 pm**

by **Joe Rich 1D**

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.

### Re: Class Lecture Work Example Question

Posted: **Sun Jul 02, 2017 10:58 pm**

by **Johana Jeon 1A**

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