Have you ever wondered if your microwave oven leaks radiation? If so, it turns out there is a pretty simple test to check the radiation 'seal' on your microwave oven. We all want to make sure we are not exposed to the rays that turn frozen foods into ready-to-eat meals in minutes.
In fact, the process of 'cooking' foods in a microwave oven is pretty interesting. Microwaves 'excite' the water molecules within the food to cause it to rapidly heat up.
As you would expect, this radiation can't be allowed to bathe your kitchen when in operation. Devices like microwave ovens must go through rigorous testing before they can be released for general use. Let's join Physics Girl as she tests whether some microwaves can, in fact, leak radiation.
The radiation test
A fascinating, if not slightly disconcerting video by Physics Girl shows us we should probably check our microwave ovens. Her simple experiment shows us that there is an easy and effective way to check the integrity of the radiation shielding on your kitchen appliance.
Microwave ovens, like cell phones, emit radiation in a specific band of EM frequencies. So you might expect that by placing your phone inside a microwave and closing the door the signal would be blocked by the microwave shell. It would also be reasonable to assume that you shouldn't be able to ring the phone once inside. But Physics Girl's test shows that with some microwave ovens you can! This was surprising, to say the least.
Faraday cages are supposed to 'shield' anything inside them from external electromagnetic fields, like electricity. They work when an electric field or other electromagnetic waves, like those from cellular phones, cause electrons in the metal to move and create an electric field to exactly oppose and cancel out the external wave or field.
More microwave ovens on the market get a deeper test
Physics Girl decided to cast her net a little wider and test her friend's different makes and models of microwaves for dodgy shielding.
She conducted the same experiment on other microwave ovens and found that some of the ovens shielded the cellular signal whilst others did not. It seemed to be a case-by-case issue.
Her next step was to test which part of the microwave was actually letting the radiation escape. Using aluminum foil to act as a near perfect Faraday cage, she wrapped her phone completely on the foil. Sure enough, no one was able to call her phone.
The next step was to wrap certain parts of the microwave oven to narrow down and seek out the 'leaky' parts. By systematically leaving parts of the microwave unwrapped they hoped to find the leak. It turned out that the door was the most likely culprit.
More radiation experiments
Next, Physics Girl employed the services of a self-professed hacker to make use of a HackRF radio transmitter and receiver for a different experiment. This device can receive and transmit signals from 1 MHz to 6 GHz. Using the device and a bona fide Faraday cage they were able to demonstrate that you shouldn't be able to call a phone shielded by one.
Next, they tested whether commonly used Wi-Fi signals can get through the microwave's door. Wi-Fi signals use a similar frequency to microwave ovens so this is an interesting test. Microwaves typically operate at around 2.45 Gigahertz, whilst cellular signals tend to be around 1.9 Gigahertz or 850 megahertz.
Sure enough, they were able to FaceTime the phone through the microwave door.
She points out that older microwave ovens can affect the quality of your domestic Wi-Fi routers and devices! Using the same detector they were also able to directly detect microwave energy outside of the microwave oven as well.
They hypothesized that the radiation could be exploiting 'holes' in the shielding of the door allowing the microwave oven to leak radiation. As Physics Girl points out, her experiments show that some microwaves do let the specific frequencies of mobile phones through, providing clear evidence that some form of radiation leakage is possible within these appliances.
Physics Girl does note that her experiment had a very small sample size, did not take into consideration the microwave oven's age or the proximity of it to a cellular tower. These variables could affect the results.
Should you be worried?
FDA regulations actually allow for a small amount of leakage from microwaves, about 5 mW/cm2. The radiation itself is non-ionising so won't damage your DNA directly, rather it will excite the water within your soft tissues.
The FDA does warn that high exposure to microwaves can lead to a painful burn. Organs like eyes and testes are particularly vulnerable because they have relatively little blood flow to carry away the heat. Also, the lens of the human eye is very sensitive to heat. High levels of microwaves could cause cataracts.
The FDA does note that this kind of damage would require a large amount of radiation.
So should you be concerned if you microwave oven leaks radiation? Well no. You are more likely to hurt yourself from a heated glass of water than the radiation itself. The radiation will not be in a high enough dose to cause you any harm.