## HW 1B.15c

$E=hv$

Jessica Chen 2C
Posts: 103
Joined: Thu Jul 11, 2019 12:17 am

### HW 1B.15c

I just directly plugged the frequency they gave us in part b into the c=λν equation, but that's not correct. How do we know when we have to take kinetic energy into account as well?

Kishan Shah 2G
Posts: 132
Joined: Thu Jul 11, 2019 12:15 am

### Re: HW 1B.15c

We know its kinetic energy, since the photon needs to contain enough energy to eject the electron from the surface as well as to cause it to move at 3.6 x 10^3 km*s^-1 . The energy involved, therefore, is kinetic energy. I was also confused at first on why we use Kinetic Energy, and in my opinion the question should be more clear on that, but we should just know it now that it has shown up.