According to Wien's displacement law, the wavelength $\lambda_m$ corresponding to maximum energy emission is given by $\lambda_m = \frac{b}{T}$. Given $b = 2.88 \times 10^6\text{ nm K}$ and $T = 5760\text{ K}$: $\lambda_m = \frac{2.88 \times 10^6}{5760} = 500\text{ nm}$ Therefore, the energy of radiation emitted is maximum at a wavelength of $500\text{ nm}$. This means $U_2$ (energy at $500\text{ nm}$) is the maximum energy among all wavelengths. Hence, $U_2 > U_1$ and $U_2 > U_3$. The correct option is $U_2 > U_1$.