Theory of Light Mirror Lens

Every day people need the light. With the light, be the light of the world so everyone can see objects around and enjoy the beautiful scenery. If there is no light, all darkness visible. People can not see anything. Thus, light is something that is very important in human life.

II.1.1 . understanding Light
Experts have long learned to know the essence of light. At first, the light is defined as a stream of particles emitted by the light -producing objects (light sources). However, another investigation states that light is a wave because light has the properties as that of the wave. In the end, they concluded that both of the above theory is that the light is propagating material and light is a wave is correct.
Humans can hear sound through the sense of hearing, the ear. Meanwhile, humans can catch the light by using the senses of sight, the eye. As sound, light is also a wave. Thus, light is a wave that can be captured by the eye.

In the 1860's, who is also an expert mathematician Physics of Scotland , James Clerk Maxwell (1831-1879) put forward the theory that light is a wave propagation generated by a combination of electric and magnetic fields . Waves generated by a combination of electric and magnetic fields called electromagnetic waves . Direction of vibration and direction of propagation of electromagnetic waves perpendicular to each other . Therefore, the electromagnetic waves propagate transversely . Electromagnetic waves can propagate in a vacuum . That's why sunlight can reach the earth's surface .

Wavelength of light determines the type of light it produces . Based on the wavelength of light can be divided into two kinds , namely :

1. Visible light is an electromagnetic wave type most famous . This light is part of the spectrum of electromagnetic waves that can be captured by the human eye . Wavelength of visible light ranges from 4 x 10-7 m ( purple ) to 7 x 10-7 m ( red ) . Outside the range of the human eye can not detect it .
2. Light is light that is not visible can not be detected by the human eye because its wavelength is outside the range that can be detected by the human eye . Examples of light is not visible gamma rays , X-rays , ultraviolet and infrared rays .

Because light propagates in a straight line , then when the light is blocked by opaque objects (dark objects), the area behind the barrier will not receive light . If there is a barrier behind the screen or wall , the wall is formed on the screen or a dark area called the shadows . The shadows can be divided into two types , namely :

1. Umbra shadows .
2. If the beam of light emitted from a small light source (can be considered as points) blocked , then there is no other part of the visible light source behind a barrier. Thus , formed a dark shadow called the umbra .Penumbra shadows .

At a relatively large light source , in addition to form as well umbra shadow blur formed called the penumbra. Penumbra can occur because some of the light beam is blocked and the source of most of the other files are still visible .

Formation shadows umbra and penumbra can be observed at the time of the eclipse , both solar and lunar eclipses. When a solar eclipse , most of the region experienced a total solar eclipse , the majority experienced a partial solar eclipse (partial  and some do not experience an eclipse . An area experiencing a total solar eclipse because the area just hit umbra shadow of the moon. In this area the sun was not visible at all . Penumbral shadow areas affected by the moon will experience a partial solar eclipse . In this region the sun is only partially visible . Getting away from the umbra shadow , the greater part of the sun is visible , so the brighter the penumbral shadow . In the areas that did not experience an eclipse , the sun was not at all deterred by the moon . The sun seemed intact .

In the event of a lunar eclipse , moon first enters the penumbral shadow of the earth so the moon looks dim . When the moon enters the Earth's umbra shadow , the moon does not appear at all . Moments later , the moon leaves the umbra shadow and back into the penumbral shadow . The moon was bright as normal after coming out of the shadows penumbra .

If the size of the light source is much larger than the barrier , it does not form a shadow umbra . The shadows are formed only a shadow penumbra . Due to the very large size of the source , then no matter where the object is behind the barrier , the parts of objects that emit light is always visible . There is no place behind the barrier that keeps the light source completely closed , except when observed at a very close distance from an obstacle .

Broadly speaking , the light has the properties as follows :

a. Is a wave and a particle .
b. Can undergo reflection .
c. Can undergo refraction .
d. Can undergo diffraction .
e. Can interference .
f. Can dispersion .
g. Can be polarized .
h. Can undergo scattering .