# Photoelectric Effect and the conversion ofPlank's constant from V.S to J.S

1. Jan 19, 2012

### Hmpca

i graphed cut-off voltage verses frequency.
when i figured out plank's constant so when i calculated the slope of the function i got 4.224x10-15. My question is how to convert V.s to J.s for the value of h

hereS the question

FINDING A VALUE OF PLANK'S CONSTANT FORM YOUR GRAPH.
calculate the slope of the graph (in V.s)
plank's constant is the slope of a graph of maximum kinetic evergy vs frequency so we need to convert cut-off coltage to maximum kinetic energy. we can use the equation.
eV=change in kinetic energy
because cut-off voltage just stops the most energetic electron.
convert the value of your slope to J.s and compare your value to the accepted value of plank's constant.

2. Jan 19, 2012

### technician

If you have plotted KEmax against frequency the units on each axis should be eV (or maybe Joules) and s^-1 (frequency unit)
Can you see what units the gradient of a graph on these axes will be?