Planets form in protoplanetary disks around young stars. As most young stars form in clusters, planet-forming disks in the vicinity of O, B stars are exposed to various levels of UV radiation. Such external UV radiation environment plays a key role in protoplanetary disks evolution affecting disk lifetime, disk properties, and planet formation. Photoevaporating protoplanetary disks (proplyds) show cometary morphology with tails pointing directly away from the ionizing star. These proplyds provide an excellent laboratory to study the direct interplay between the external UV radiation and protoplanetary disk dispersal. Recent observational and theoretical studies suggest that external photoevaporation is a dominant mechanism of disk dispersal, and their disk lifetimes are expected to be very short compared to the age of clusters. Most of the known proplyds are located in the Orion star forming regions. We present a census of proplyds in three star forming regions in the Orion A and B clouds, which represent strong and intermediate UV environments for ages ranges of <0.5?2 Myr: Orion Nebula Cluster (ONC), NGC 1977, and NGC 2024. These clusters provide strong (ONC, NGC 2024) and intermediate (NGC 1977) UV radiation environments. NGC 2024 provides the youngest age among the three regions (age <0.5-1 Myr). NGC 1977 provides the weakest UV environment, where the major ionizing source is a B1 star, while mid-late O stars are present in ONC and NGC 2024. Using multi-wavelength imaging and spectroscopic observations, we present an up-to-date census of proplyds, properties of protoplanetary disks and central stars, and young stellar populations in these clusters to probe the effects of UV radiation environments during the critical time for giant planet formation. We present kinematic studies of the proplyds and the non-proplyd young stars in ONC and NGC1977, and discuss the origin and lifetime problem of proplyds.