In a hydrogen atom, the electron is in nth excited state. It comes down to the first excited state by emitting 10 different wavelengths. The value of n is

Number of possible emission lines are n(n - 1)/2 when an electron jumps from nth state to ground state. In this question, this value should be (n - 1) (n - 2)/2.Hence, 10=(n−1)(n−2)2Solving this, we get n = 6.