Penumbral imaging is a technique used by nuclear engineers for imaging objects (e.g., X-rays and lasers) that emit high-energy photons. In IEICE Transactions on Information & Systems (Apr. 2005), researchers demonstrated that penumbral images are always degraded by noise, where the number Y of noise events occurring in a unit of time follows a Poisson process with mean l. The signal-to-noise ratio (SNR) for a penumbral image is defined as SNR = μ/σ , where μ and σ are the mean and standard deviation, respectively, of the noise process. Show that the SNR for Y is √λ.