The Bases of the Optics


6. Spectrum of Light:

White light

White paper

The incidence of light is refracted according to Snellfs Law (Refraction Law). .

Thereafter, it goes out again through the prism with constant refraction ratio at the opposite surface boundary of the prism and hits the surface of white paper. In case the light is white light and when it arrives on the white paper, the incidence of light can be observed as 7 colors of rainbow which are consisted by the different wavelengths.

This phenomena is defined as Dispersion of light.

As illustrated above, the band lined with wavelengths of the light is called as  Spectrum of light and the same through the prism is called as dispersed Spectrum.

The different refraction ratios for each light create this phenomena.

yThe Reasons why we can see the rainbowz

We suppose the water drop is a whole ball and sunshine lighten the water drop with paralleled lights. The incidence of light through the center of the ball is gOh and the light gah has some distance of ghh from gOh. The incidence of light into the ball is refracted and arrives inside surface of the ball and then some portion of the light goes out from the ball.

Meanwhile, the reflected light goes forwards through the drop and it is again reflected a part after arrivals on the surface of the drop.

In case the angle between the light gaf h going out from the ball with the refraction and the incidence of the first light gah is understood as „q, the „q is decreased in the first stage according to the value of g h h and thereafter it is increased. Therefore, there exists g h h when„qis getting to the minimum size. If color is different, refraction ratio is different and „q is naturally different depending on each color. The refraction ratio of Red is 42‹and the ratio of purple is 40.5‹

Therefore, the beautiful rainbow is observed because of the reasons mentioned above. We , however, occasionally observe another pale rainbow outside the ordinary rainbow. The ordinary rainbow appears at 41‹over half peak angle of the cone and the second one appears of the direction at 52‹which is created with double inside reflection of the water drop. The orders of colors are reversible between the first rainbow and the second one

7. Colors of Light:

(1)Three Prime Color of Light:

In case whole colors can be obtained by mixing with
appropriate ratios of three different colors,
these three different colors are called
as three prime colors of light

Three prime colors consist with Red (wavelength 700 nano-m)
Green (wavelength 546 nano-m) and Blue (wavelength 436 nano-m).

(1)Mixing of Light Color:

‡@       If we mix three prime colors with same ratio, we can obtain white color.
@@@@Red + Green + Blue => White

‡A@@@If we obtain white color by adding two colors, it is called as complementary 
@@@@colors against other.
@@@@ Red + Blue and Purple =>white
@@@@Yellow + Blue and Purple => white

Green + Red and Purple => white

  (3) Color Aberration of Lens:(The details shall be discussed in next edition.)
@@@By dispersion of light through the lens, the phenomena seeing in dim light and
@@@coloring of a material object is called as color aberration of lens. In case a band of
@@@white paralleled lights goes into the lens, each color does not focus to the one point
@@@but each color focuses to different points according to its wavelength.
@@@If you look at something far away, using a cheap binoculars, this is the phenomena
@@@which you can see coloring of surround of the material object.

white light






white light

8. Color of Material objectF

(1)Color of Material object
@A part of white light projected to the material object reflects on the surface as it
   is, but some of the light enters a little inside of the surface and is selectively
   absorbed. The balance of color light not absorbed goes out from the surfaces with
   diffused reflection. These mixed colors are called as Color of Material Object.
   It is ,therefore, understood that the material object has no specific color
   but we have various views because of spectrum composition of lighting.

(1) Mixing of Color Paint:

‡@The colors of paint are color of the material
@object. If color paints are mixed, the balance color
  which are not absorbed by constituent paints
   is appeared

@Red + Yellow => Orange
@ Yellow + Blue => Green 
@ Blue + Red => Purple

     ‡A@Three colors of Red, Yellow and Blue are Three Prime Colors of paint.

To be continuedcc..

Next edition will be discussed on the following subject

(The renewal date will be cccccc.)

  * Interference of light



If you have interest of the story of optics lens Vol.001 and 002, kindly visit to our web site to

VOL.001.The Bases of the Optics
VOL.002.The Bases of the Optics