If we calculate shortest wavelength for paschen we take n2= infinity?

No, the shortest wavelength for the Paschen series occurs when the electron transitions from the n=3 energy level to the n=4 energy level. This transition results in the emission of a photon with the shortest wavelength in the Paschen series. The formula for calculating the wavelength of this transition is given by:

1/λ = R(1/3^2 - 1/4^2)

where R is the Rydberg constant.

Yes, when calculating the shortest wavelength for the Paschen series in the atomic emission spectrum of hydrogen, we take n2 = infinity. This is because the Paschen series corresponds to transitions from higher energy levels (n > 3) to the n2 = 3 energy level. Therefore, as n2 approaches infinity, the wavelength of the emitted photon approaches its minimum value, which corresponds to the shortest wavelength in the Paschen series.