JEE Mains Model Paper 12

For a transition from n = p to n = q in hydrogen, photon energy = ε1 = 13.6 (

1

q2

−

1

p2

) eV
For a transition from n = a to n = b in helium,
photon energy = ε2 = 4 × 13.6 (

1

b2

−

1

a2

) eV = 13.6 ((

2

b

)2 - (

2

a

)2) eV
For the photons of same energy to appear in the spectra

1

q2

−

1

p2

= (

2

b

)2 - (

2

a

)2
This will be satisfied if b = 2q and a = 2p