An electron spends about 10^-8s in an excited state before it drops to a lower state by emiting a photon. How many revolution does an electron in an n=2 bohr orbit make in 1.00*10^-8s? (ans_8.23*10^6 revolution)

velocity in any orbit = (2.18*10⁶)/n m/s

 V₂ = (2.18*10⁶)/2 m/s

radius of any orbit =  (52.9)*10^-12n² m

r₂ = (52.9*10^-12)4 m

time in which electron completes one revolution is

T = 2pir₂/V₂

T =12*10^-16                    

let it completes n crevolution so total time taken = n(12*10^-16)

 n(12*10^-16) = 10^-8

    n = 8.23 * 10⁶ revolutions