to be equal to 1.55 times 10 to the minus 19 joules.

Positive value because photons have positive energy.

So now you take that energy of the photon and

you calculate the wavelength of that light that was emitted.

Pause, select your answer and make sure you look for your units carefully.

Select your answer and then resume.

[SOUND] Well, did you select 1280?

Now this is 1280 nanometers.

That's what I asked it for in.

Now if you calculated it and you got 1.28 times 10

to the minus 6 meters, okay, you didn't convert it on over to nanometers.

And that would be the correct answer.

Now if you got that and you want to move on, go ahead.

Otherwise you can watch what I do to come up with that wavelength.

I would use E equals h nu, and I could calculate my frequency.

And then c equals lambda nu to calculate my wavelength, or

I can combine them and do it in one equation.

To combine them I'm going to take the equation on the right and

I'm going to solve for nu.

So c over lambda is equal to nu, and I'm going to plug that into the nu I see here.

E equals hc over lambda.

Then I'm going to solve for lambda, lambda equals hc over E.

And then I'll plug my values in, lambda is equal to 6.626

times 10 to the minus 34 Joules times seconds.

3.00 times 10 to the 8 meters per second.

And the E was 1.55 times 10 to the minus 19 Joules.

So when you calculate all of that, you're going to get this number here,

1.28 times 10 to the minus 6 meters, which is this many nanometers.

Remember 1 nanometer equals 10 to the minus 9 meters.