– 5 –
Microwaves and How They Work
Microwaves are a form of high frequency radio
waves similar to those used by a radio, including
AM, FM and CB. They are similar to a television
where the radio waves are converted to a picture on
the screen. However, microwaves are much shorter
than radio waves; approximately twelve centimetres
wave length. Electricity is converted into microwave
energy by the magnetron tube (which is the heart of
the microwave oven).
From the magnetron tube, microwave energy is
transmitted to the oven cavity. The microwaves are
converted to heat in the food. The microwaves enter
from the outside of the food and travel through the
food losing half of their power every two to three
centimetres. Continued cooking to the centre occurs
by conduction.
Although pacemakers used to be affected by
microwaves (as well as by other radio waves), they
are now shielded and are not bothered by these
interferences. This allows people with pacemakers
to sit calmly by their radio or television and cook with
microwave ovens.
When microwaves come in contact with a substance,
any one or combination of three things may occur.
They can be:
1. REFLECTED
2. TRANSMITTED
3. ABSORBED
Re
fl
ection:
Metal substances REFLECT microwave energy and
because there is no absorption, there is no heating.
This is why the oven interior is either stainless
steel or epoxy-coated steel. This ensures that the
microwaves are kept inside the cavity and evenly
distributed throughout the food with the help of the
turntable.
Transmission:
Such substances as paper, glass and plastic
TRANSMIT microwave energy and do not become
hot except from food. Because these substances
do not re
fl
ect or absorb microwave energy, they are
ideal materials for microwave cooking containers.
Absorption:
Food contains moisture and will ABSORB microwave
energy, which causes the moisture molecules
within the food to vibrate at an incredible rate
(2,450,000,000 times per second). Friction, created
by the vibration, produces heat energy which is
conducted throughout the food.
Installation and General Instructions
(continued)
7.
COOKING TIMES given in the Cooking Guide
section are APPROXIMATE.
Factors that may
affect cooking time are preferred degree of
moisture content, starting temperature, altitude,
volume, size, shape of food and utensils used.
As you become familiar with the oven, you will be
able to adjust for these factors.
8. It is better to
UNDERCOOK RATHER THAN
OVERCOOK foods.
If food is undercooked, it
can always be returned to the oven for further
cooking. If food is overcooked, nothing can be
done. Always start with minimum cooking times
recommended.
9. Extreme care should be taken when cooking
popcorn in a microwave oven. Cook for minimum
time as recommended by manufacturer. Use
the directions suitable for the wattage of your
microwave oven. NEVER leave oven unattended
when popping popcorn.
10. When heating food in plastic or paper containers,
check the oven frequently due to the possibility of
ignition.
11. The contents of feeding bottles and baby food jars
are to be stirred or shaken and the temperature
is to be checked before consumption, in order to
avoid burns.
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