Compactness of $T$ implies that of $T^{*}$. Since $\lambda \neq 0$ and $\overline {\lambda} \notin \sigma_p (T^{*})$ it follows from compacteness of $T^{*}$ that $T^{*}-\overline {\lambda}$ is invertible. Hence its kernel is $\{0\}$ and the orthogoanl complement of the kernel is $\mathcal H$.
Compactness of $T$ implies that of $T^{*}$. Since $\lambda \neq 0$ and $\overline {\lambda} \notin \sigma_p (T^{*})$ it follows from compacteness of $T^{*}$ that $T^{*}-\overline {\lambda}$ is invertible. Hence its kernel is $\{0\}$ and the orthogoanl complement of the kernel is $\mathcal H$.