Unit 4 Inventions and Inventors
Lesson 13
Exercise 1.2
Microwave ovens are used by
millions of families every day.
Many of you may have a microwave oven
in your home.
they are so simple to use.
The food is placed in the oven.
The oven is programmed for the correct time
and then switched on.
In just a few minutes,the food is heated
and then taken out of the oven and served.
Easy
But do you know how a microwave oven works?
Professor wilkins is here to explain.
Well,it's quite simple,really.
Micrwave ovens use microwaves to heat food.
The microwaves are absorbed by the food and
they are turned into heat.
One advantage of microwave ovens is that
they are very quick.
Why is this?
Microwave ovens can cook food quickly
because all the food is heated at the same time
And here's another questions for you.
Why doesn't the plate get hot,
when I cook something in my microwave?
Ah,that is because
the microwaves are absorbed by the food
but they are not absorbed by things
like plastic or glass.
That is why plates and cups don't get hot.
Exercise 2.2
Today,photocopiers are found everywhere
and millions of papers are copied every day.
How does a photocopier work?
An Original paper is placed face down
on a special glass plate
and the lid is closed.
Different choices are chosen
--for example,how many copies
or what size of copy
--and then the START button is pressed.