Its 10.2 eV or 2.55 eV.

R= .529 *(n^2/Z )

n = no. Of orbit

Z = atomic no.

Given R1/R2 = 4:1

n1^2/n2^2 = 4:1

n1/n2 = 2:1

Among 1st 4 orbits

n1 = 4 or 2

n2 = 2 or 1

If n1 = 4 then n2 =2

Or n1= 2 then n2 = 1

Use energy equation then

E = -13.6 *(Z^2 / n^2 )

For case 1 ∆E = 2.55 eV

For case 2 ∆E = 10.2 ev

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