Two lines show where each bar ends.
Bigger or smaller?
Ponzo illusion
Which yellow bar is longer?
They are the same length, though the top one looks longer.
Why? The rails meeting in the distance tell your brain that the top bar is farther away. Something far away that still looks this big must be huge, so your brain makes it look longer.
Picture: Drawn by Science Playground · Wikipedia(opens in a new tab)