German scientist Döbereiner was one responsible for grouping elements into triads based on most notably atomic mass, many of which can be found in the periodic table to be in a pattern (for example <span><span>Iron </span><span>Cobalt </span><span>Nickel, elements 26, 27, 28)</span></span>
Intensity has no affect on whether or not the photoelectric effect occurs. The determining property is frequency and since frequency and wavelength are inversely proportional, wavelength matters as well. If a frequency of light can't cause the photoelectric effect to happen, no matter what the intensity is, the light can't make it happen.
I hope this helps. Let me know in the comments if anything is unclear.
C a giraffe that eats the leaves off trees
