GP's comment said 100Hz because that's what you get from full-wave rectification of 50Hz mains, so they were talking about that. It'd be 120Hz in countries that

GP's comment said 100Hz because that's what you get from full-wave rectification of 50Hz mains, so they were talking about that. It'd be 120Hz in countries that use 60Hz mains (e.g. in North America).