## Homework Problem B.5

$E=hv$

Savannah Mance 4G
Posts: 107
Joined: Fri Aug 30, 2019 12:17 am

### Homework Problem B.5

In this problem, the given information is that a y-ray has energy of 140.11 keV and I'm supposed to find the wavelength. I know I'm supposed to use Einstein's equation. But, what is keV? What is this unit? I've never seen it before so I have no idea how to convert it or if I even have to.

christabellej 1F
Posts: 109
Joined: Sat Aug 17, 2019 12:17 am

### Re: Homework Problem B.5

KeV is a unit of energy. It is equivalent to 1000 eV because of the prefix kilo. From there, you can convert this unit to another energy unit - Joules by using the constants and equations sheet. 1 eV is equivalent to 1.6022*10^-19 J, so you can then use stoichiometry to convert KeV to Joules. After that, you can use the 2 equations we learned: E = hv and c = (wavelength) (frequency) to find the overall wavelength.

Kayli Choy 2F
Posts: 100
Joined: Sat Aug 24, 2019 12:17 am

### Re: Homework Problem B.5

An electron-volt (eV) is a unit of energy that is equal to the energy an electron gains after being accelerated across 1 volt. This unit is typically used when discussing energy on an atomic/sub-atomic level (very small amounts of energy).