Welcome to Clip from Spiral logo

Interactive video lesson plan for: How Do Microwave Ovens Work?

Activity overview:

They’re convenient, ubiquitous and easy to use. But how do these things work, exactly? What do people mean when they say a microwave cooks food inside out?

Join HowStuffWorks as we answer engaging, everyday science questions, demystifying the amazing world around you.

Learn more at

Share on Facebook:
Share on Twitter:
Visit our site:

Love ‘em or hate ‘em, there’s no denying: Microwave ovens are super convenient. They can heat food much more quickly than a conventional oven – although not always with the same results.

But how do they… you know. Work?

Yeah, yeah. Microwaves. Sure. But what the heck are those? Good question. Microwaves are a type of wave on the electromagnetic spectrum, sandwiched between radio waves and infrared radiation. In the case of microwave ovens, the most common wave frequency is roughly 2,450 megahertz (2.45 gigahertz).

Waves in this frequency range have an interesting property: They're absorbed by water, fats and sugars. Once absorbed, they're converted directly into atomic motion -- heat.

These waves have another convenient property: They're not absorbed by most plastics, glass or ceramics.

Metal, however, does reflect microwaves, which is why it’s a bad idea to leave a spoon in your cheese dip when the oven’s on.

You’ll often hear people say microwave ovens cook “from the inside out”, right? That’s the key to the speed. Think about it like this: Let’s say you’re baking a cake in a conventional oven. Normally you would bake it at 350 degrees F (177 degrees C) or so, but this time you accidentally set the oven at 600 degrees F (316 degrees C). The outside of the cake will burn before the inside even gets warm, and you’ll have ruined somebody’s birthday.

In a conventional oven, the heat has to migrate by conduction from the outside of the food toward the middle. Hot, dry air on the outside evaporates moisture, so the outside can be crispy and brown – like the crust on bread - while the inside is moist.

In microwave cooking, the radio waves penetrate the food and excite water and fat molecules more or less evenly throughout. No heat has to migrate toward the interior by conduction. There's heat everywhere, all at once, because the molecules are all excited together.

There are limits, though. Microwaves penetrate unevenly in thick pieces of food (they don't make it all the way to the middle), and there are also "hot spots" caused by wave interference, but you get the idea. The heating process is different because you are "exciting atoms" rather than "conducting heat."

Inside a microwave oven, the air is at room temperature, so there's no way to form a crust. That’s why microwavable pastries or hot pockets sometimes come with a little sleeve made out of foil and cardboard. The sleeve reacts to microwave energy by becoming very hot. This exterior heat lets the crust become crispy as it would in a conventional oven.


Tagged under: brainstuff,brain stuff,howstuffworks, stuff works,science,technology,microwave,microwave oven,cooking,food tech,Ben Bowlin,Oven (Culinary Tool),Food,microwaves,electromagnetic spectrum, microwaves work, microwaves work, microwave,oven,kitchen

Clip makes it super easy to turn any public video into a formative assessment activity in your classroom.

Add multiple choice quizzes, questions and browse hundreds of approved, video lesson ideas for Clip

Make YouTube one of your teaching aids - Works perfectly with lesson micro-teaching plans

Play this activity

1. Students enter a simple code

2. You play the video

3. The students comment

4. You review and reflect

* Whiteboard required for teacher-paced activities

Share on:

Share How Do Microwave Ovens Work? on Google+ Share How Do Microwave Ovens Work? on Twitter Share How Do Microwave Ovens Work? on Facebook Pin How Do Microwave Ovens Work? Email How Do Microwave Ovens Work?

Ready to see what else Spiral logo can do?

With four apps, each designed around existing classroom activities, Spiral gives you the power to do formative assessment with anything you teach.


Carry out a quickfire formative assessment to see what the whole class is thinking


Create interactive presentations to spark creativity in class

Team Up

Student teams can create and share collaborative presentations from linked devices


Turn any public video into a live chat with questions and quizzes

1000s of teachers use Spiral to deliver awesome, engaging activities that capture students' understanding during lessons.

Now it's your turn Sign up

Spiral Reviews by Teachers and Digital Learning Coaches

Review of Spiral by teacher: Kathryn Laster @kklaster

Tried out the canvas response option on @SpiralEducation & it's so awesome! Add text or drawings AND annotate an image! #R10tech

Review of Spiral by teacher: Room 220 Math Stars @3rdgradeBCE

Using @SpiralEducation in class for math review. Student approved! Thumbs up! Thanks.

Review of Spiral by teacher: Miss Ord @ordmiss

Absolutely amazing collaboration from year 10 today. 100% engagement and constant smiles from all #lovetsla #spiral

Review of Spiral by teacher: Adam J. Stryker @strykerstennis

Students show better Interpersonal Writing skills than Speaking via @SpiralEducation Great #data #langchat folks!

Review of Spiral by teacher: Dr Ayla Göl @iladylayla

A good tool for supporting active #learning.

Review of Spiral by teacher: Brett Erenberg @BrettErenberg

The Team Up app is unlike anything I have ever seen. You left NOTHING out! So impressed!

Get the Clip Chrome Extension & Create Video Lessons in Seconds

Add Clip to Chrome