Answer:
1.32×10^16 hz
Explanation:using Rydberg equation:
1/λ = RH •Z^2[ (1/n1) - (1/n2) ]
RH = Rydberg constant = 1.097 x 10^7 m-1)
n1 and n2 = energy levels (n2 >n1)
Z = atomic number = 4
Substitute
1/λ = 1.097×10^7 • 4^2[ (1/2) - (1/4) }
λ = 2.28 × 10^-8m
From the equation of light
C= fλ
C=3×10^8m/s
f = 3×10^8/2.28×10^-8
f = 1.32×10^16 hz