Rainbow---Formation and New Insight

Project done by :

Yitong Wang [email protected]

Sophia Yiu [email protected]

Gaohong Liu [email protected]

Hanlun Zhou [email protected]

Final Project Physics 001 Section 001

Connection Between Rainbow and

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Our Course

 A rainbow is an optical and meteorological phenomenon that is caused by both reflection and refraction of light in water droplets in Earth's atmosphere, which is related to our lecture on Light & Reflection and Refraction.

In class, we learned some basic principle and theories about light, reflection and refraction. The principle of rainbow is reflection and refraction of the light. The principle of a rainbow is exactly connected to our lecture.

The formation of a rainbow

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Rainbow

is that sunlight refraction and reflection happened but takes form with certain angle irradiation on water-drop. Rain has been all over in the queen , the sky small water-drop, this is one kinds of natural triple prism. , when sunlight permeates water-drop since refraction composes in reply an opposite direction effect, be become seven colored light , can see the beautiful arc as long as the sun angle is appropriate quilt decomposing. If only having tiny water-drop in air drying, or the sky, cannot only be capable to do the rainbow taking form. ( sources: Principle that rainbow forms http://www.shvoong.com/exact-sciences/1645853-principle rainbow-forms/)

 Come to say water-drop is increasingly big , rainbow belt is increasingly narrow , the color is increasingly distinct the sort; Whereas, water drop is increasingly small, rainbow belt is increasingly broad , the color is dim. Sometimes, we can see the sky have two strip rainbow: A bar shouts the host rainbow , a vivid shade , inside is purple , outside is red; Another a bar shouts subsidiary rainbow , inside is red , outside is purple, The rainbow color is thinner. This phenomenon is a reason since sunlight permeates two time of refraction happened and reflecting when water-drop.

 A rainbow is most often viewed as a circular arc in the sky. An observer on the ground observes a half-circle of color with red being the color perceived on the outside or top of the bow. Those who are fortunate enough to have seen a rainbow from an airplane in the sky may know that a rainbow can actually be a complete circle. Observers on the ground only view the top half of the circle since the bottom half of the circular arc is prevented by the presence of the ground (and the rather obvious fact that suspended water droplets aren't present below ground). Yet observers in an airborne plane can often look both upward and downward to view the complete circular bow. ( sources: Rainbow Formation---The Physics Classroom http://www.physicsclassroom.com/class/refrn/Lesson-4/Rainbow Formation)

 The circle (or half-circle) results because there are a collection of suspended droplets in the atmosphere that are capable concentrating the dispersed light at angles of deviation of 40-42 degrees relative to the original path of light from the sun. These droplets actually form a circular arc, with each droplet within the arc dispersing light and reflecting it back towards the observer. Every droplet within the arc is refracting and dispersing the entire visible light spectrum.

 As described above, the red light is refracted out of a droplet at steeper angles towards the ground than the blue light. Thus, when an observer sights at a steeper angle with respect to the ground, droplets of water within this line of sight are refracting the red light to the observer's eye. The blue light from these same droplets is directed at a less steep angle and is directed along a trajectory that passes over the observer's head. Thus, it is the red light that is seen when looking at the steeper angles relative to the ground.

Similarly, when sighting at less steep angles, droplets of water within this line of sight are directing blue light to the observer's eye while the red light is directed downwards at a more steep angle towards the observer's feet. This discussion explains why it is the red light that is observed at the top and on the outer perimeter of a rainbow and the blue light that is observed on the bottom and the inner perimeter of the rainbow.

New Insight

 Before researching on rainbow, we don’t know that reflection and refraction of light in water droplets are reasons why a rainbow forms. Now we know more about reflection, refraction and how rainbow forms.

 Through learning about rainbow, we not only learn something about rainbow itself, but also learn something about light. Now we can explain some other nature phenomena by using the theory of light.

 We know different angle and degree of refraction is the reason why a rainbow has different colors. Reflection and refraction are so amazing.

Reference and Citations

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Rainbow---Wikipedia http://en.wikipedia.org/wiki/Rainbow

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Principle that rainbow forms

http://www.shvoong.com/exact-sciences/1645853 principle-rainbow-forms/   Rainbow Formation---The Physics Classroom http://www.physicsclassroom.com/class/refrn/Lesson 4/Rainbow-Formation

Thank you!