The central wavelengths of three low loss windows commonly used in optical fiber communication are ( ), ( ) and ( ）. 光纤通信中常用的三个低损耗窗口的中心波长分别是（）、（）和（）
The central wavelengths of three low loss windows commonly used in optical fiber communication are ( ), ( ) and ( ）. 光纤通信中常用的三个低损耗窗口的中心波长分别是（）、（）和（）
Which is NOT the correct description about Laser? A: It stands for Light Amplification by Stimulated Emission. B: It’s a beam of light energy. C: All the light waves in a laser are emitted in the same rhythm. D: The light waves in a laser are of different wavelengths.
Which is NOT the correct description about Laser? A: It stands for Light Amplification by Stimulated Emission. B: It’s a beam of light energy. C: All the light waves in a laser are emitted in the same rhythm. D: The light waves in a laser are of different wavelengths.
Why is more earth's heat blocked from escaping with more carbon dioxide in the atmosphere A: Carbon dioxide prevents the sun's energy from going back into space. B: Carbon dioxide radiates the sun's energy onto the earth. C: Carbon dioxide produces more heat in the atmosphere. D: Carbon dioxide takes in the sun's energy at infra-red wavelengths.
Why is more earth's heat blocked from escaping with more carbon dioxide in the atmosphere A: Carbon dioxide prevents the sun's energy from going back into space. B: Carbon dioxide radiates the sun's energy onto the earth. C: Carbon dioxide produces more heat in the atmosphere. D: Carbon dioxide takes in the sun's energy at infra-red wavelengths.