## 1.17

$c=\lambda v$

Chloe Orsini 1K
Posts: 32
Joined: Fri Sep 28, 2018 12:18 am

### 1.17

For this question why do we multiply by four? I know to find the frequency we multiply R by (1/n1^2)-(1/n2^2). But in the answer it is also multiplied by four. I think it has to do with z^2 in the question, but i'm still confused.

AustinGrove3B
Posts: 53
Joined: Fri Sep 28, 2018 12:23 am

### Re: 1.17

This is because for He +, z is equal to 2. So 2^2 =4. So the equation is 4 * R (energy difference). But I believe Dr. Lavelle said he would only test us on hydrogen, which has a z=1, so you can ignore that part of the equation.