An article in Sensors and Actuators A: Physical [“Characterization and Simulation of Avalanche PhotoDiodes for Next-Generation Colliders” (2011, Vol. 172(1), pp. 181–188)] considered an avalanche...

An article in Sensors and Actuators A: Physical [“Characterization and Simulation of Avalanche PhotoDiodes for Next-Generation Colliders” (2011, Vol. 172(1), pp. 181–188)] considered an avalanche photodiode (APD) to detect charged particles in a photo. The number of arrivals in each detection window was modeled with a Poisson distribution with a mean depending on the intensity of beam. For one beam intensity, the number of electrons arriving at an APD follows a Poisson dis- tribution with a mean of 1.74 particles per detection window of 200 nanoseconds.

a. What is the mean and variance of the time for 100 arrivals?
b. What is the probability that the time until the fifth particle arrives is greater than 1.0 nanosecond?