How Scooby doo identified Refrigerator even with a mirror door?

Dogs have an excellent sense of smell, and Scooby is a dog and known to be a food lover / connoisseur. It is very likely he smelt the food in the refrigerator, or in the hands of the people who used the door of the refrigerator.

A dog's sense of smell is 900 times better than a human's sense of smell, the dog's hearing is 90 times better than a human's hearing, a dog's sight is not very good, but they can detect movement a lot better than what humans can, and last of all: Dogs can reach a speed of 64k/h.

Scooby would have been able to easily see through the mirror window and detect movement.

Dogs can also filter out periferall noises to focus on one particulat noise and when they do hear a noise, their sense of direction of where the noise is coming from is very accurate.