What is light?

To understand light, we must first understand the properties of waves.

The components of a wave are amplitude, frequency, period, and wavelength. Amplitude is the difference in height between the low and high points of a wave. Frequency is the number of oscillations per unit time. Wavelength is the distance between the top of the wave and the top of the wave.

The speed of a wave can be expressed as frequency multiplied by wavelength.

Electromagnetic waves are transverse waves that propagate by alternating electric and magnetic fields.

A wave is a repetitive, periodic motion that travels from one location to another through a medium (such as water).

Light is an electromagnetic wave and is a wave form of electric and magnetic fields.

Light is fastest in a vacuum and slows down in the presence of a medium. (299,792,458 m/s)

The speed of light is the maximum value of the speed that all energy, matter, and information in the universe can have, and according to recent theories, it is also the speed of gravitational waves. Massless particles and fields (including electromagnetic radiation such as light) travel at c, and in inertial systems, particles and waves travel at c, regardless of the speed of the observer.

Direction of Electromagnetic wave

* image formation (Irradiance = intensity)

I = power(W)/area(m2) = 단위 시간 당 에너지

All EM wave has same speed in vacuum, but have different energy (E = hv = hc/ㅅ)

전자기파(빛)의 속도는 C로 일정하지만, wave length에 따라서 energy가 결정된다.

전하(전자)가 일정하게 움직이지 않으면(가속) 그 전기력선 결의 찢겨짐으로 인해서 전자기파가 발생한다.

 

* Electric Dipole (전기쌍극자)

+전하에서 -전하로 전기장이 흘러간다. 그 선들을 전기력선이라고 한다. 그 contour는 같은 전위를 같는다. 

전기쌍극자가 서로간의 거리가 가까워졌다 멀어졌다 하면서 진동을 한다면 서로 간의 전기장의 세기는 세졌다가 약해졌다를 반복하게 됨.

 

* Refraction Index

 n = the speed of light in vaccum / the speed of ligth in matter

    = c / v > 1 (일반적으로 1보다 크다)

 

* Electromagnetic waves are the spread of an electric field caused by the acceleration of an electric charge.