쉐도잉 연습: Intro to Scanning Electron Microscopy (SEM) - YouTube로 영어 말하기 배우기
C2
Welcome to the Technological Institute at Northwestern University.
127 문장
문장이 너무 짧거나 길면 Edit를 눌러 조정하세요.
1
Welcome to the Technological Institute at Northwestern University.
2
Today we are going to tour the Northwestern Atomic and Nanoscale Characterization Experimental Center,
3
or the Nuance Center.
4
We're going to start in the EPIC lab,
5
which stands for Electron Probe Instrumentation Center.
6
Here at EPIC, scientists from all over the world use high-powered electron microscopes to characterize a large range of different materials.
7
Scientists such as geologists who study rocks,
8
biologists who study cells, and even scientists who look at individual atoms and teeth use these electron microscopes.
9
But what is an electron microscope?
10
How is it different from a traditional light microscope you see in labs all over the country?
11
What even is a microscope?
12
Let's take a tour of the EPIC facility to learn more about the vast and growing field of microscopy.
13
So what is a microscope?
14
Let's dissect the word.
15
The root scope means to watch or to see,
16
and the prefix micro means extremely small.
17
Together we can see that a microscope is an instrument
18
that allows someone to see a very small object and comes in many shapes and sizes.
19
The microscope you're probably most familiar with is an optical or light microscope.
20
It was developed in the 1600s by scientists who made glasses.
21
are made out of glass lenses that bend light.
22
This makes objects seen through a lens look much bigger or smaller than they actually are.
23
Telescopes, binoculars, microscopes, and cameras are all examples of objects that use glass lenses.
24
In this microscope, a light source travels through a series of glass lenses.
25
The first lens is the eyepiece lens.
26
This makes the image bigger that's produced by what's called the objective lens.
27
The objective lens is the highest power lens that's closest to the sample.
28
Some microscopes have a condenser lens which concentrates the light beam before it travels through your sample.
29
The sample is placed on the stage above the condenser lens and below the objective lens.
30
Light then travels up through the lenses reaching your eye.
31
What we're looking at now is a fly's wing in the light microscope.
32
You can start to see the texture
33
and even the hairs on the fly's wing that you couldn't see before with the naked eye.
34
With the objective lenses on an optical microscope you can magnify the object up to 2,000 times.
35
The way this microscope works is very similar to the microscope you have in your pocket.
36
Light is energy that travels in waves of different wavelengths ranging from about 400 to 700 nanometers.
37
This is visible by the human eye.
38
Using light, we can make objects appear thousands of times larger than they actually are.
39
But what if we want to see something millions of times larger?
40
Something like a cell or a virus?
41
Another form of energy comes as an electron beam.
42
An electron is a very small negative charged particle that is part of an atom.
43
A beam of electrons has a wavelength several orders of magnitude smaller than visible light.
44
In order to use an electron beam to create an image,
45
we have to use a special microscope called an SEM,
46
or a scanning electron microscope.
47
Here is one of our SEMs.
48
It has an electron source at the top of the column
49
that travels through the microscope column itself and into the specimen chamber where the image is created by a series of detectors.
50
You cannot bend an electron beam with glass so you have to use special electromagnetic lenses.
51
The lens set up in electron microscope is very similar to a light microscope.
52
It has a light source or an energy source at the top,
53
a condenser lens, an objective lens,
54
and the sample is kept in a slightly different spot inside the specimen chamber.
55
The image you see from light microscope is projected directly onto your eye.
56
The electron microscope image is processed and displayed on a computer screen.
57
An electron microscope sample is prepared on an aluminum pin stub using special carbon glue or carbon tape.
58
We then coat the sample with metal,
59
something that the electrons can pass through like a filament in your light bulb.
60
If the electrons cannot pass through your sample,
61
charging artifacts can make your image look really messy.
62
Adding a layer of metal can help dissipate the charge buildup on the surface of the sample,
63
making your image look much better.
64
Once the samples are ready,
65
they are inserted into the stage inside the SEM.
66
Inside the SEM you can see the special detectors we use to create the image,
67
as well as the objective lens pull piece that houses the objective lens and where the beam comes out.
68
Now we can close the door and pump down the chamber.
69
We have to remove all the air molecules inside the specimen chamber.
70
If the electron beam interacts with air,
71
it will scatter and not make it to the sample.
72
By removing the air molecules,
73
we create an unobstructed path directly to the sample surface.
74
Now we are ready to go.
75
Let's turn on the beam and see how this works.
76
We move the stage under the pole piece to move around the sample.
77
But how is the image being created?
78
As the beam hits the sample,
79
it interacts and creates secondary electrons that get sucked up by the secondary electron detector inside the chamber.
80
As it scans across the sample,
81
the signal is collected for each point or pixel and creates your image.
82
This is the same fly we were looking at before.
83
Unlike light microscopy,
84
the signal you see in this image is from the surface of the specimen it does not travel through the specimen.
85
Now we can see details on the wing that we couldn't see with the light microscope.
86
Look at the hairs on the surface of the fly's legs.
87
With an electron microscope like this SEM,
88
you can magnify the image up to one million times.
89
This is much greater than the 2,000 times of an optical microscope.
90
This is the fly's leg.
91
We also saw this with the light microscope,
92
but what we didn't see are these hairs on the surface.
93
The electron microscope allows you to achieve resolutions that you are unable to see with a light microscope.
94
Sometimes the charge buildup on the surface of a sensitive sample can make the sample move.
95
Here's the fly's compound eye.
96
Have you ever seen this before by looking at a fly with the naked eye?
97
Can you guess what this is?
98
These tiny squares are about 1 micron wide.
99
That's 1,000th of a millimeter.
100
And makes up the pixels in your cell phone camera.
101
Finally, this is the back end of a spider.
102
It almost looks like the texture in your fingerprint.
103
Another type of signal ejected from the specimen during the electron beam interaction are x-rays.
104
With x-rays, we can determine the chemical composition of a material, like this penny.
105
You can see that this penny is composed of copper and zinc.
106
Since 1982, pennies were no longer made of pure copper and were made of copper-coated zinc.
107
Have you ever noticed that Abraham Lincoln is sitting inside the Lincoln Memorial on a penny?
108
Some other electron microscopes have an ion beam that can mill away your sample or deposit metal on the surface.
109
So what is the difference between a light microscope and an electron microscope?
110
The major difference is that light microscopy uses light as an energy source,
111
whereas electron microscopy uses a beam of electrons.
112
Light microscopy is easy to use,
113
easy to prepare samples, and you can view live specimens.
114
You can also see them in color,
115
but you get much lower resolution and magnification.
116
With an electron microscope you get high resolution,
117
up to 1 million times magnification,
118
with a larger depth of field,
119
but you only get black and white images.
120
You also have to do more involved sample preparation,
121
and you cannot view live specimens.
122
You also need an electrically conductive sample.
123
The invention of the electron microscope changed the world of science forever.
124
It is used in many fields such as biology,
125
medicine, chemistry, geology, material science, and even forensics.
126
Thank you for visiting the EPIC lab at the Nuas Center.
127
We hope that you'll come back sometime and explore inner space with us.
앱 다운로드
당신이 말하는 모든 문장을 AI가 채점
TRENDING
인기 동영상
이 비디오로 말하기 연습을 해야 하는 이유
이번 비디오에서는 주사전자현미경(SEM)에 대한 소개를 다룹니다. 과학의 최전선에서 일하고 있는 연구자들이 사용하는 이 고급 장치는 마이크로스코프의 발전을 이해하는 데 도움이 됩니다. 영어 쉐도잉을 통해 이 비디오의 내용을 반복하고 따라 함으로써, 과학 관련 어휘와 특정 발음을 익히는 데 큰 도움이 됩니다. 특히, shadow speech 방법을 활용하면 발음, 억양, 그리고 자연스러운 말하기를 학습하는 데 더 큰 효과를 볼 수 있습니다.
문법 및 맥락에서의 표현
- What is a microscope? - 이 문장은 과학적 개념을 쉽게 설명하는데 효과적입니다. 질문 형식을 통해 청중의 흥미를 유도합니다.
- It was developed in the 1600s by scientists who made glasses. - 과거 시제 사용이 중요하며, 과거의 사건을 설명하는 데 적합합니다.
- Light then travels up through the lenses reaching your eye. - 이 문장은 과학적 원리를 묘사하는 과정에서 현재 진행형을 사용하여 흐름을 자연스럽게 만듭니다.
- Using light, we can make objects appear thousands of times larger. - 인과 관계를 명확하게 드러내며, 일반적 진리를 제시하는 데 유용한 구문입니다.
이러한 표현들을 반복적으로 연습함으로써, 영어 회화 연습에 있어 자연스러운 문장 구조를 익힐 수 있습니다.
자주 발생하는 발음 함정
비디오에서 주의해야 할 몇 가지 발음 요소가 있습니다. microscope와 electron 단어는 특히 앞뒤 자음이 연결되며, 부정확하게 발음할 경우 뜻이 달라질 수 있습니다. 또한 wavelength의 경우, 강조할 부분을 잘 조절하지 않으면 청중이 이해하기 어려울 수 있습니다. 이러한 어려운 단어들을 집중적으로 연습하면 shadow speak 능력이 향상되어 보다 명확하게 의사소통할 수 있습니다.
쉐도잉이란? 영어 실력을 빠르게 키우는 과학적 방법
쉐도잉(Shadowing)은 원래 전문 통역사 훈련을 위해 개발된 언어 학습 기법으로, 다언어 학자인 Dr. Alexander Arguelles에 의해 대중화된 방법입니다. 핵심 원리는 간단하지만 매우 강력합니다: 원어민의 영어를 들으면서 1~2초의 짧은 지연으로 즉시 소리 내어 따라 말하는 것——마치 '그림자(shadow)'처럼 화자를 따라가는 것입니다. 문법 공부나 수동적인 청취와 달리, 쉐도잉은 뇌와 입 근육이 동시에 실시간으로 영어를 처리하고 재현하도록 훈련합니다. 연구에 따르면 이 방법은 발음 정확도, 억양, 리듬, 연음, 청취력, 말하기 유창성을 크게 향상시킵니다. IELTS 스피킹 준비와 자연스러운 영어 소통을 원하는 분들에게 특히 효과적입니다.
☕ 커피 한 잔 사주기
ShadowingEnglish는 여러분의 지원 덕분에 100% 무료로 운영됩니다. 서버 및 AI 유지 비용이 많이 듭니다. 여러분의 커피 한 잔이 큰 힘이 됩니다! ��