The answer would be it will be longer than the 656.3 nm. The reduced mass of positronium is less than hydrogen so the photon energy will be a reduced amount of for positronium than for hydrogen. So this will mean that the wavelength will be lengthier.
Answer: Mass affects the weight of an object with the effects of gravity.
Weight is the measure of the force of gravity on an object's mass, while mass is the measure of how much matter there is in an object.