2020년 3월 15일 일요일

01.04 - 파장(Getting on the Same Wavelength)

01.04 - 파장(Getting on the Same Wavelength) [커세라 강의페이지]



[00:07] It's impossible to discuss the concept of a black hole without first delving into the details about light or electromagnetic radiation.

천체를 다루면서 빛 혹은 전자기 복사를 언급하지 않을 수 없다. 빛조차 없는 깜깜한 블랙홀을 다루는데도 예외는 아니다. 이번 편에서 다루는 이야기는 매우 기초적인 사항이므로 동영상 강의를 듣는 것문으로도 충분하다. 이번 강의에 등장하는 주요 어휘에 대해서만 정리해본다.

1. Light or Electromagnetic radiation
2. Black Hole, completely dark
3. Wavelength
4. Wave and Frequency
5. Energy of Photon
6. Sound, another analogy of wave; pitch or frequency
7. Color of light vs. Pitch of sound
8. Sound: Longitudinal wave
9. Spectrum of sound: infrasonic & ultrasonic
10. Electromagnetic wave: speed of light in vacuum, characterized by frequency of wavelength
11. Longitudinal or transverse wave
12. Spectrum of Electromagnetic wave



13.Photon: Individual particle of light

- This is the same as saying that light is quantized, each photon is a small discrete packet of energy.
- The energy of a photon is related to its wavelength and frequency and therefore its color.
- With a beam of light, there are trillions of photons, each with their own energy.
- The energy that a photon carries is proportional to its frequency and inversely proportional to its wavelength.

14. X-Rays, high frequency, carrying higher energy, can cause tissue damage
15. Radio wave, lower frequency, can be used for telecommunication safely

16. Wave-Particle Duality

We've talked about light in terms of waves, discussing features like wavelength and speed; also particles or photons. So which is it, are photons waves or are they particles?

And it took scientists a long time to work this out, with arguments debating the nature of light and matter in the 1600s through till the early 1900s. This idea is known as wave-particle duality.

The duality being that light can act either as a wave or as a particle depending on the situation you are considering.

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