why electromagnetic wave theory was not able to explain the results of black body radiation and photoelectric effect???

please answer at +1 level.....

it is probably because of dual nature of light... as said by feynman, we try to imagine things as we see.. so we think that light can show only one property, but it shows both wave and particle nature..

Because scientists at that time considered that light travelled in form of waves....but with dual nature of matter....scientists now could explain the stuff...