Sign In | Sign Up | Help | Invite    
Advanced Search Ask A Question Community Recent Changes
My:             Contributions   
Contributors
{for ul in pageInfo.page}
${ul.nickName}
{var al = toBreakWord(ul.adUrl,18)} {if ul.adSentence !=''}${ul.adSentence}
{/if} {if ul.adUrl !=''}${al}
{/if}
 
{/for}
Earn Free Advertising   +   Earn Money By Writing What You Know at WISTEME.COM
Question Discussion History

Edit
    Question ID:   12968         Current Version: 1
Question: How will light behave after entering the bottom of a cone shaped prism?
Category: Science > Physics
Keywords: enter, cone, shape, prism, behave, light
Type: how
Rating:(0 ratings)    Views: 259    Discussions: 0   In Watch Lists: 1  

 
    Answer:
Light entering the bottom of a cone-shaped prism can do one of several things, depending on the angle of the prism and the coatings applied to it. As long as the light rays bounce off the inner sides at an angle greater than the critical angle (sine(n2/n1), where n2 and n1 are the indices of refraction of the prism and the material surrounding it), then you will get total internal refraction, and the inside surface will look like a perfect mirror. Now several things can happen.

If the angle of the cone is such that after a few bounces the light ray hits the side at an angle less than the critical angle (measured from the normal to the surface), then the light ray can escape through the side of the prism. For a glass prism in air, the critical angle is about 41.8 degrees. Since the index of refraction in glass depends on the frequency, different colors will have a different critical angle and will be dispersed just as in a standard equilateral prism. There are pictures on the internet of glass cone prisms in museums of historical optics which were used to produce a circular spectrum. Coating the sides with various compounds or submerging the prism in oil or water, which have a different index of refraction than air, will change the critical angle and either reduce or increase the amount of total internal reflection. This would let you tailor the prism to allow the light to escape after only a few (or no) bounces, or to keep bouncing nearly all the way to the tip.

If the tip of the cone is nipped off at a point where the light coming in the bottom is still seeing total internal reflection, all the light emerges from the narrow end. This is the idea of a conical optical fiber. The light is concentrated, but it is diffuse, not focused. It won't be easy for a lens to work with it but if you just needed a wide beam squashed down to a narrower spot at some point, that'll do it.

Another possibility is to leave the cone intact but to silver the side like a mirror. This makes the side reflective at any angle so that the beam can never get out that way. As the beam bounces down the cone the reflection angle steepens until eventually it has to turn around and start bouncing back out again. The result is that the cone returns the beam back to the original direction. This has applications in laser ranging for distance measuring where you want to send a beam to a target and have it come directly back to you so you can measure the travel time.

Source: NASA
Read more questions from WISTEME through
     Add to MSN Add to My AOL
 Rate this Question
   Add to Groups   Add to Watch Lists   Share Question
                          
 
    More Readings :
[QID:8332]    Does light have a mass?  
[QID:7956]    What are earthquake lights? Are they real?  
[QID:6108]    What are lighting timer controls?  
[QID:6095]    What are lighting photosensor controls?  
[QID:4934]    How to safely light a firework?  
[QID:8451]    What is infrared light?  
[QID:6128]    How can I best use daylight for my home illumination?  
[QID:6117]    What are the types of lighting controls?  
[QID:6094]    What are lighting motion sensor controls?  
[QID:6081]    What do I need to know about lighting maintenance?  
     Question ID:  ${question.id}         Current Version:  ${question.version}

{for qh in questionHistory} {if qh.status == 'r'} {else} {/if} {/for}
Version Contributor Date (ET) Voting
${qh.version} ${qh.nickName} ${qh.date} Rejected
${qh.version} ${qh.nickName} ${qh.date} {if qh.status != 'c'} {if qh.status == 'a'} Approved {else} {if qh.rstatus == 'c'} On-going {else} Pending {/if} {/if} {else}   {/if}
Start a New Topic
ID Topics Replies Latest Post (ET)
{if dlist!=null} {for d in dlist} {/for}
${parseInt(d_index)+1} ${d.sentence} ${d.replyNum} ${d.lastestDate}
{else}
No discussion topic.
{/if}
Label Name:
 
Group Name:
 
 
{else}
     You have no group.
{/if}
Advertisements
{if advertisements.length > 0} {else} {/if}
{for ad in advertisements}
${ad.adTitle}
${ad.adSentence}
${ad.adUrl}
{/for}

Home | About Us | Terms of Use | Privacy Policy | Browse Questions | RSS Feed

Copyright ©2010 WISTEME LLC. All Rights Reserved.