system
Given the following post, respond as if you're commenting on Reddit:
human
Why do microwaves cook/heat things faster than ovens, when ovens reach higher temperatures?

e.g stick a Hot Pocket in the microwave and you’re good to go in about 2 1/2 minutes, but put it in the oven, and it takes about 10-15. According to the box, anyway.
gpt
A microwave works by directly causing heating in the food itself, which is a much more direct and efficient process. First a magnetron generates microwaves, which has some unintended energy loses that go to heating the magenetron. Next, the microwaves go into the cavity, and are absorbed by and heat the food. The air and microwave safe dish are transparent, so they don't absorb any of the energy and heat up. The walls are reflective, so they also don't heat up. So beyond the losses in the magnetron, the energy goes pretty much entirely into the food and it's the only thing that is heating up. 



An oven is much more indirect. Firstly, an element is intentionally heated up to a few thousand degrees. That alone is a loss of energy simply to heating it up so much. The element then transfers heat either by conduction to anything it touches o by thermal radiation. The thermal radiation is much like microwaves, however the walls and dishes aren't transparent or reflective. Therefore a lot of energy goes into heating them to a few hundred degrees. The conduction happens to the air, which itself has to be heated to a few hundred degrees. Then the air has to move around the over by convection to heat the food. The walls of the oven are also quite a lot of surface, so a lot of heat is lost to the outside. Compare this to the much smaller surface area of the food itself you are heating in a microwave. In the end, it is a lot more inefficient as instead of slightly heating a magnetron in addition to the food, you've heated a substantial amount of metal, air, ceramic to a few hundred degrees as well as bleeding off more what to the environment. 


A hot pocket is say 100g, and we'll say that's just water. So to heat that from say 0C freezing to 100C boiling, you need 42,000 joules of energy (4.2 J per g per C). You microwave consumes around 1000W of electrical power, so 1000 joules per second. Ideally, your hot pocket could be heated in 42 seconds. Due to losses, mostly in the magenetron, it takes 2.5 minutes. So about 30% of your electrical energy actually went into heating your food. 


Your over on the other hand, let's say is also 1000W (though that's more like a toaster over). Assuming it's on broil, ie the elements are always on, it's using 1000W for 10 minutes. So that's about 8% of your electrical energy actually going into the food, the rest just heats the over and the air. 




However, the oven is usually even slower. You usually don't use broil, but a set temperature, so the oven elements aren't on the whole time. They do this because both the thermal radiation and air heat just the skin of the food, potentially burning the outside and leaving the inside cold. The inside only heats by conduction of the beat from the surface, which takes time. As such, the elements turn on and off to maintain a lower temperature, slowing the cooking but allowing more even cooking. The microwaves however can penetrate further into the food, cooking it more evenly without the need for downtime to let the inside cook. In essence, the microwave is always 1000W, but the 1000W over may only be on half the time, being 500W on average. 


So it's not just inefficiency of an oven heating a bunch of unnecessary mass in addition to your hot pocket, but also the oven needing to hold back on full power to avoid burning the outside of the food. Less power and less efficiency, means slower cooking times. However, a microwave isn't a magical quick and efficient solution to all cooking, as often the longer cooking time and slight burning of the surface that an oven causes are desirable. That's why your microwave hot pocket is soggy while the oven one is crispy.