Answer:
n=5
Step-by-step explanation:
Applying the Rydberg's equation
hc/l= RH[(1/nf^2)-(1/ni^2)
Let l= wavelength= 3745×10^-9m
h=6.63×10^-34 , c= 3.0×10^8, RH= 2.179×10^-18
Substitute into the Rydberg's equation and simplify
(6.63×10^-34×3×10^8)/3745×10^-9=2.179×10^-18(1/nf^2 -1/8^2)
0.024= 1/nf^2 -0.0156
0.024+0.0156= 1/nf^2
0.0396= 1/nf^2
nf^2= 25.3
Take square root of both sides
nf= 5.02=5