Tripping the Light Fantastic

Introduction

This is just a short discussion about light — yes, I’m talking about the kind that shines. Did you know that some light is visible to the human eyes and some light is not?  To illustrate this, I must introduce you to a friend of mine named Roy G. Biv.  If that sounds like a strange name, you’re right! It’s not a real person; it’s a mnemonic!  This name helps us remember the colors of the visible light spectrum.

The Visible Light Spectrum

14888_discussions.jpg?width=238You have seen this spectrum before.  It’s called a rainbow!  Can you see Roy G. Biv to the left here?

Red, orange, yellow (Roy) Green (G.) Blue, indigo, violet (Biv)

14889_discussions.jpg?width=367Can you find ROY G BIV in this actual rainbow spectrum?

 

 

 

The Invisible Light Spectrum

Did you know that there is a lot more light on either side of this visible spectrum (below the red side and above the violet side)?  The light spectrum below the red is called infrared (infra-red or IR).  The light spectrum above or beyond the violet is called ultraviolet (UV).  UV light is further divided into UV-A and UV-B light.  So why do we care about IR and UV light if we cannot see them?  Well, they have special uses if we know how to harness them.

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For example, special binoculars can be used to “see” IR light, allowing us to see in the dark. These are called night vision glasses. The military uses these for night combat.

 

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UV Light

UV light from the sun is the light that burns our skin when we get a sunburn. Tanning salons are places where you can lie in a tanning booth, which uses UV light to tan you inside without sunlight.  UV light can not only burn your skin but it can also damage your retinas (“projector screen”) at the back of your eyes.  Sunglasses are specially made to block UV-A and UV-B light to protect your eyes from this damage.  Even some clothes are designed to block UV rays to minimize your chances of getting sunburned through their thin material.

You may ask: If light is made of all these visible colors, why can’t I see them all the time? Good question. When all these colors are blended together, they form what we call white light, which is the normal sunlight we see outside. Being a blend of all the colors, it is transparent and thus invisible to us.

So if we have white light, you might guess that we must have something called black light, huh? You would be correct.  We use the term black light to refer to UV-A light. You can buy black light bulbs in novelty and party stores. Some nightclubs use black light to produce a snazzy (cool, neat, fancy) effect.  UV light makes white things and fluorescent things shine very brightly in the dark.

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Self-Assessment

  1. For night combat, a soldier needs to take night vision goggles because they can “see” (IR/UV/visible/black) light.
  2. Many American ladies love to soak their bodies in tanning salons for hours to get that “perfect tan”. They do this by lying under (IR/UV/visible/black) light rays.
  3. Sunglasses need to block what kind of light to protect your eyes from retina damage? (IR/UV/visible/black)
  4. What is the fourth color from the top of a rainbow? (don’t look!)
  5. What does “ultra” mean?
  6. What does “infra” mean?
  7. Why is IR light called IR light?
  8. Can you name a few household items that may use IR or UV light?
  9. What does the idiom “trip the light fantastic” mean?
  10. Have you ever “tripped the light fantastic” under a black light before?
  11. Did you learn anything new from this discussion? If so, list keywords to let me know what was new to you (for my curiosity).
  12. Can you share with me any little-known fact about any aspect of light that you might be aware of?

Bonus!  Song: You Light Up My Life

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