The wave length of light emitted in the visible region by $$He^+$$ ions after collisions with H atoms is

A

$$6.5 \times 10^{-7}$$ m

B

$$5.6 \times 10^{-7}$$ m

C

$$4.8 \times 10^{-7}$$ m

D

$$4.0 \times 10^{-7}$$ m