In photo electric effect ,if electrons escape, shouldn't that leave the metal positively charged ??. How does it maintain its electrical neutrality ? And if it doesn't , shouldn't the work function increase as a positive metal piece would pull electrons more strongly and more energy would be required.
Metals are conductors. As electrons escape, new electrons easily flow from ground into the metal to maintain neutrality. If you have an insulator in vacuum, it does begin to gain a positive charge as electrons are removed, which causes an increase in the apparent workfunction.