Question

what is de-Broglie wavelenght associates with the hydrogn electron in its third orbit

Answer 1

k.e = 1/2 mv²

for v we can use the equation wavelength = h/mv

h is Planck's constant = 6.626 ÷ 10³⁴ joule second

also convert 4.8 picometer into metre = 4.8/10¹²