Q18. The longest wavelength associated with Paschen series is : (Given $R _ { H } = 1.097 \times 10 ^ { 7 } \mathrm { SI }$ unit)\\
(1) $3.646 \times 10 ^ { - 6 } \mathrm {~m}$\\
(2) $1.876 \times 10 ^ { - 6 } \mathrm {~m}$\\
(3) $2.973 \times 10 ^ { - 6 } \mathrm {~m}$\\
(4) $1.094 \times 10 ^ { - 6 } \mathrm {~m}$