NTNUJAVA Virtual Physics LaboratoryEnjoy the fun of physics with simulations! Backup site http://enjoy.phy.ntnu.edu.tw/ntnujava/
September 29, 2020, 08:53:50 am
 Welcome, Guest. Please login or register.Did you miss your activation email? 1 Hour 1 Day 1 Week 1 Month Forever Login with username, password and session length

 Home Help Search Login Register
To be a citizen of the world. ...Wisdom

 Pages: [1]   Go Down
 Author Topic: Physics of rainbow (EJS version)  (Read 12373 times) 0 Members and 1 Guest are viewing this topic. Click to toggle author information(expand message area).
Fu-Kwun Hwang
Administrator
Hero Member

Offline

Posts: 3085

 : 1 users think this message is good1 Physics of rainbow (EJS version) « Embed this message on: February 12, 2010, 06:23:04 pm » posted from:Taipei,T\'ai-pei,Taiwan

When white sunlight is intercepted by a drop of water in the atmosphere, some of the light refracts into the drop, reflects from the drop's inner surface, and then refracts out of the drop.
As with the prism, the first refraction separates the sunlight into its component colors, and the second refraction increases the separation. The result is the rainbow.

The following applet shows many light rays heading for the water drop (white circle).
Because the incident angle are not the same for different incoming ray, the second refraction ray coming out at different angle.
The question is why we always saw the rainbow at a fix angle relative to the sun ray?

Embed a running copy of this simulation

Embed a running copy link(show simulation in a popuped window)
Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop. This work is licensed under a Creative Commons Attribution 2.5 Taiwan License
• Please feel free to post your ideas about how to use the simulation for better teaching and learning.
• Post questions to be asked to help students to think, to explore.
• Upload worksheets as attached files to share with more users.
Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!

You can click the "real intensity" checkbox to find out the relative intensity for different paths.
You can drag the black square near the left side of the simulation to drag those rays up and down.

You might notice that intensity for incoming rays are not the same. It is indicated that the cross section are not the same for different ray.
If the ray is off by the center of the water drop by distance b, and the rasius of the circle is R.
The incident angle $\theta$, where $\sin\theta=b/R$, the effective cross section is proportional to $\cos\theta$

If the index of refraction is n, the refracted angle $\phi$, where $\sin\phi=b/R/n$ ( i.e. $sin\theta= n \sin\phi$).

If the intensity of incoming ray is $I$, then the intensity for the reflected ray(s wave) is $I_r=\frac{\sin^2(\theta-\phi)}{\sin^2(\theta+\phi)} I$ and the intensity for refracted light is $I'= I-I_r$

The above formulas are used to calculate the intensity for different ray.
I hope the above simulation can help you understand more about the physics of rainbow.

You are welcomed to check out physics of Rainbow for more in depth discussion about rainbow.

You can find more information about rainbow from http://www.atoptics.co.uk/bows.htm
 rainbow.gif (13.98 KB, 721x390 - viewed 766 times.) Logged
 Pages: [1]   Go Up
To be a citizen of the world. ...Wisdom
Jump to:

 Related Topics Subject Started by Replies Views Last post physics of Rainbow « 1 2 » Optics Fu-Kwun Hwang 40 596881 February 06, 2020, 08:47:21 am by adamschule85 Manufactured Rainbow Optics Harbinger 1 18347 February 20, 2006, 10:52:58 am by Fu-Kwun Hwang Physics of rainbow (EJS version) optics ahmedelshfie 5 12267 February 16, 2020, 10:33:11 pm by visasoulii9 Physics of rainbow (EJS version) Questions related to EJS ahmedelshfie 4 9548 May 12, 2010, 11:30:28 pm by ahmedelshfie EJS version of oscilloscope Electronic Fu-Kwun Hwang 2 14080 May 14, 2020, 02:59:24 pm by lookang
Page created in 0.709 seconds with 22 queries.since 2011/06/15