By Gauss's Law:
\[ \oint \vec{E} \cdot d\vec{A} = \frac{q_{\text{in}}}{\varepsilon_0}. \]
For a spherical shell, the electric field \( E \) is constant across the surface area:
\[ E \cdot 4\pi R^2 = \frac{\sigma \cdot 4\pi R^2}{\varepsilon_0}. \]
\[ E = \frac{\sigma}{\varepsilon_0}. \]
Thus, the electric field at the surface of the spherical shell is:
\[ \boxed{\frac{\sigma}{\varepsilon_0}}. \]
Let $ P_n = \alpha^n + \beta^n $, $ n \in \mathbb{N} $. If $ P_{10} = 123,\ P_9 = 76,\ P_8 = 47 $ and $ P_1 = 1 $, then the quadratic equation having roots $ \alpha $ and $ \frac{1}{\beta} $ is: