Quick questions on The photoelectric effect and photons: WACE Year 12 Physics Unit 4

Light is emitted and absorbed in discrete packets called photons, each carrying energy

The maximum kinetic energy can be measured with a stopping voltage $V_0$, the reverse potential difference that just halts the fastest electrons,

The single most examined graph in this topic plots maximum kinetic energy $E_{k,\max}$ against photon frequency $f$. From $E_{k,\max}=hf-W$ this is a straight line of the form $y=mx+c$, so the gradient equals Planck's constant $h$ and is the same for every metal. The horizontal intercept (where $E_{k,\max}=0$) is the threshold frequency $f_0=W/h$, and the vertical intercept is $-W$. Different metals therefore give parallel lines (same gradient $h$) shifted horizontally according to their work function: a metal with a larger work function has a higher threshold frequency and its line crosses the axis further to the right.