Photoelectric effect

[HERculina]

Has anyone done question 6 exercise 11.4 the dual nature of light.
Can someone explain why/how the max kinetic Energy versus f graph is drawn. I looked at worked solutions but it made me more confused 
And what is a trough and a crest in waves?
Thanks.

[HERculina]

Question is from Heinemann heinemann textbook

[Lasercookie]

The gradient of the graph is Planck's constant. The magnitude of the y-intercept of the graph is the work function.
The x-axis is frequencies, the y-axis is stopping voltages / energy.

Blue - -

UV  - -

So you have two points.



That's fairly close to the value of Planck's constant in eV s.  (note that )

For the y-intercept, if you're given a graph in the exam, a quick way is to just extrapolate the line and see where it would hit the x-axis. However, we now know the gradient, so we could just sub two points and solve for W







edit: forgot about your second question

And what is a trough and a crest in waves?

crest = bit with the maximum, trough = bit with the minimum

[HERculina]

Thank you so much laseredd! I finally understand this q. Now