Question

In hydrogen sample all electrons are in 5th excited state
find wavelength of longest line

Answer 1

For single electron species,

λ1=RZ2(n121−n221)

where, R = Rydberg constant =  1.097×107×10−9nm−1=1.097×10−2nm−1

For Hydrogen atom, Z = Atomic number = 1

For Balmer series, n1 = 2 and for longest wavelength in Balmer series, minimum energy transition is to be considered because wavelength is inversely proportional to Energy.

So, n2 = 3

∴λ1=1.097×10−2nm−1×12(221−321)

⇒λ=656nm

Hope it helps you ,if yes,mark as BRAINLIEST.