Given the value of Rydberg constant is 107m-1, the waves number of the lest line of the Balmer series in hydrogen spectrum will be: (1) 0.025�104m-1 (2) 0.5�107m-1 (3) 0.25�107m-1 (4) 2.5�107m-1

Answer: (3)

We know that:

λ₁= R(1/n₁²−1/n₂²)

For last line Balmer’s series,

n₁₌2 and n₂=∞

λ₁= 10⁷(1/2²−1/∞²)

λ₁= 0.25×107m⁻¹