# Homework Help: Planck's constant calculation

1. Apr 21, 2005

if you are given the stopping potential and the threshold frequency, how do you calculate Planck's constant from it?

2. Apr 22, 2005

### dextercioby

HINT:Assume all the energy of the electron/accelerated particle is converted into an energy of the photon...

Daniel.

3. Apr 22, 2005

ive used E=hf
hf= Kmax + PHI
Kmax=eV

all it does is bring me round and round

4. Apr 22, 2005

### dextercioby

Hold on a second.Are talking about Bremsstrahlung,or photoelectrical effect...?I though u meant the former,but apparently i was wrong.Usually there's the plot KE vs incoming photon's frequency and u find "h" from the slope...

Daniel.

5. Apr 22, 2005

we are given a graph of stopping potential (y-axis) vs frequency (x-axis) thats it

6. Apr 22, 2005

the stopping potential hits 0 at threshold frequency of 43.9 e13 Hz

7. Apr 22, 2005

### dextercioby

Well,the stopping potential is

$$V=\frac{KE_{particle}}{q_{particle}}$$

Either way,u need the slope of that line.

Daniel.

8. Apr 22, 2005