北师大初中英语九年级Unit 4-13（MP3+LRC）

[00:01.26]Unit 4 Inventions and Inventors

[00:05.02]Lesson 13

[00:10.56]Exercise 1.2

[00:14.46]Microwave ovens are used by

[00:16.53]millions of families every day.

[00:18.99]Many of you may have a microwave oven

[00:21.23]in your home.

[00:22.79]they are so simple to use.

[00:24.76]The food is placed in the oven.

[00:27.46]The oven is programmed for the correct time

[00:29.84]and then switched on.

[00:32.42]In just a few minutes,the food is heated

[00:35.22]and then taken out of the oven and served.

[00:37.97]Easy

[00:39.39]But do you know how a microwave oven works?

[00:42.58]Professor wilkins is here to explain.

[00:45.95]Well,it's quite simple,really.

[00:48.85]Micrwave ovens use microwaves to heat food.

[00:53.31]The microwaves are absorbed by the food and

[00:56.86]they are turned into heat.

[00:59.78]One advantage of microwave ovens is that

[01:01.98]they are very quick.

[01:03.96]Why is this?

[01:05.80]Microwave ovens can cook food quickly

[01:08.92]because all the food is heated at the same time

[01:13.29]And here's another questions for you.

[01:16.31]Why doesn't the plate get hot,

[01:18.43]when I cook something in my microwave?

[01:21.60]Ah,that is because

[01:23.87]the microwaves are absorbed by the food

[01:27.46]but they are not absorbed by things

[01:29.72]like plastic or glass.

[01:32.49]That is why plates and cups don't get hot.

[01:40.01]Exercise 2.2

[01:43.43]Today,photocopiers are found everywhere

[01:46.69]and millions of papers are copied every day.

[01:50.60]How does a photocopier work?

[01:52.94]An Original paper is placed face down

[01:55.88]on a special glass plate

[01:58.12]and the lid is closed.

[02:00.38]Different choices are chosen

[02:02.55]--for example,how many copies

[02:05.17]or what size of copy

[02:07.25]--and then the START button is pressed.

[02:08.08]