Answer:
[tex]2p\rightarrow 1s[/tex]
Explanation:
The energy of transition of [tex]3p\rightarrow 1s[/tex] is greater as compared to [tex]2p\rightarrow 1s[/tex] as there are more quantum levels which leads to more energy.
Also, considering the expression as:
[tex]E=\frac {h\times c}{\lambda}[/tex]
Where,
h is Plank's constant having value [tex]6.626\times 10^{-34}\ Js[/tex]
c is the speed of light having value [tex]3\times 10^8\ m/s[/tex]
[tex]\lambda[/tex] is the wavelength
Wavelength is inversely proportional to Energy. Thus, the transition which has lower energy corresponds to higher wavelength.
Thus, answer - [tex]2p\rightarrow 1s[/tex]
