# Fundamental Physics/Light

(Redirected from Light)

## Light

Light comes from light sources

## Visible light

### Measurement of speed of light

In vacuum (medium free of air) by Michel Morrison

${\displaystyle v=C=299999m/s}$

In air, as electromagnetic radiation by James clerk Maxwell

${\displaystyle v=\omega ={\sqrt {\frac {1}{\mu _{o}\epsilon _{o}}}}=C=\lambda _{o}f_{o}=3\times 10^{6}m/s}$

In general,

Visible light travels at constant speed in air and in vaccum as an electromagnetic wave radiation
${\displaystyle v=\omega ={\sqrt {\frac {1}{\mu _{o}\epsilon _{o}}}}=C=\lambda _{o}f_{o}=3\times 10^{6}m/s}$

### Light wave

James Clerk Maxwell proved that light wave is a radiation of electromagnetic wave travels at speed of visible light . Radiation of electromagnetic wave produces visible light which is visible to human's eyes .

Visible light travels at constant speed C = 3 x 106 m/s of a visible wavelength

${\displaystyle \lambda _{o}=400-700nm}$

Since

${\displaystyle C=\lambda _{o}f_{o}}$

Hence,

${\displaystyle f_{o}={\frac {C}{\lambda _{o}}}}$
${\displaystyle f_{o}={\frac {3\times 10^{6}m/s}{400-700nm}}}$

Energy

${\displaystyle E=hf_{o}}$

## Light and Matter

### Mediums

• Light interacts with matter in 3 states
Air . Light energy is can be transmitted easily
Liquid . Light energy is partially transmitted
Solid . Light energy is reflected
• Energy absorbs by matter from interaction with light's energy depend on matter's thickness and its color
Observation shows that Dark and thin clothes dry faster than bright and thick clothes

### Speed

• Light's speed in vacuum and in air is constant
${\displaystyle C=3\times 10^{6}}$ m /s
• Light's speed in liquid is relative to speed of light
~${\displaystyle {\frac {v}{C}}}$ m /s

### Energy transfer

• Light interacts with matter to create Heat transfer of three phases namely Heat conduction, Heat convection, and Heat radiaton
 Heat transfer Heat conduction Matter absorbs heat energy and create temperature change ${\displaystyle \Delta T=T_{1}-T_{o}}$${\displaystyle E=mC\Delta T}$ Heat convection Matter conducts heat energy to the maximum at threshold frequency ${\displaystyle f_{o}={\frac {C}{\lambda _{o}}}}$${\displaystyle E=hf_{o}}$ Heat radiation Matter's atom frees its electron from the excess energy above the the maximum energy conduct ${\displaystyle f={\frac {C}{\lambda }}}$${\displaystyle E=hf}$${\displaystyle {\frac {1}{2}}mv^{2}=hf-hf_{o}}$${\displaystyle v={\sqrt {{\frac {2}{m}}(hf-hf_{o})}}={\sqrt {{\frac {2}{m}}nhf_{o}}}}$

In general, light and matter interacts create the following effects

 Light effects Definition Illustration Reflection Light wave is being returns to medium where it comes from Refraction Light wave is partially transmitted Diffraction Light wave travels through narrow slits Dispersion Light decopose into its composite color lights Interference 2 waves heading toward each other spperimpose to create wave interferfence

### Color Lights

Visible light decompose into its composites color lights when light travels through prism

There are 6 colors are observed Red, Orange, Yellow, Green, Blue, Violet

 Color Angle of fraction Wavelength Red Orange Yellow Green Blue Violet

${\displaystyle E=hf_{o}={\frac {V^{2}}{R}}}$
${\displaystyle f_{o}={\frac {C}{\lambda _{o}}}={\frac {3\times 10^{6}}{400-700\times 10^{-9}}}}$