Answer:
electron
Explanation:
The energy for particle in a box is given by:
[tex]E=\frac{n^2 h^2}{8mL^2}[/tex]
for the system in ground state, n =1
Since, the boxes are identical, L is same for all the three particles.
h is Planck's constant.
Since energy is inversely proportional to wavelength, therefore
[tex]\lambda \propto m[/tex]
[tex]m_e<m_p<m_\alpha[/tex]
[tex]\Rightarrow \lambda_e<\lambda_p<\lambda_\alpha[/tex]
Thus, electron has the longest wavelength.