## light problem

Alondra Juarez section 1E
Posts: 47
Joined: Fri Sep 29, 2017 7:03 am

### light problem

A compound emits light with energy of 4.60 X 10^-19 J per photon. What is the wavelength of the light wave emitted by the compound in nanometers?

I know that for this problem I would have to use the formula E=hc/λ and plugged in the constants and rearranged the equation in which now I got λ= h/E and the answer I got was [4.32 X 10^-7] but I'm not to sure how I'm supposed to turn it into nanometers? I'm not to sure how to do the conversion

Sara Veerman-1H
Posts: 31
Joined: Fri Apr 06, 2018 11:05 am

### Re: light problem

So right now, you have the answer in meters. Nanometers is 10^(-9) meters so you can calculate (4.32x10^-7m)x(1nm/[10^-9]m). Which would give you 432.x10^-9m or 432nm. Hope this helps.

Posts: 31
Joined: Fri Apr 06, 2018 11:03 am

### Re: light problem

In general, conversions can be kind of tricky, and so I have this method of using dimensional analysis in order to guarantee I do the conversion correctly.

Let's say I'm trying to convert from meters to nanometers, and I have $4.3 \times 10^{-7}$ meters. I know that 1 nanometer is 10^-9. So, I can set up my conversion as seen below, and that will give me my answer in nanometers!

$4.3\times 10^{-7} m \times \frac{1 nm}{1\times 10^{-9}m}$

This way, you can just plug the above into a calculator, and if you cancel out the units, you're left with nanometers!

Hope this helped!