Said the science teacher do her science class, "Do you see what I see?"
Okay, okay so we probably can't break into chorus right now, but our title does highlight the focus of this post. We have finished our reading about how the eye sees visible light in terms of different wavelengths. This post will go in depth about how light interacts with the objects that we see.
First let's get 3 terms out of the way: transparent, translucent, and opaque.
Objects that are transparent --> glass, window, water bottle, clear wrap
(You are able to see right through the object once light interacts with it.)
Objects that are translucent --> sheer material, wax paper
(You are able to see that something is behind this type of material, but may not always be able to make out every aspect of the object because as the light passes through it is being scattered throughout.)
Objects that are opaque --> suitcase, handbag, construction paper, comforter, desk, school portrait, aluminum foil, concrete)
(These objects either reflect light or absorb it. As stated in last week's post, objects that absorb light energy usually convert that energy to thermal energy)
Are these clouds opaque, translucent, or transparent?
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| (c) M. Prince, 2012 |
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| (c) M. Prince, 2012 |
Now, how exactly are we able to see the things that we see?
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| (c) M. Prince, 2012 |
Once light shines on an object, our eyes gather and focus the light so that we may be able to see it. Eyes are able to
transmit,
refract, and respond to different wavelengths of light. This small section of light that we can see is visible light. Our
lenses help us to focus on an object. Light is
refracted (bent) from an object to the
cornea of our eye. The light then passes through the pupil and the lens. The
iris that surrounds our
pupil opens and closes to direct the amount of light we take in through our eyes. Once the light hits the
retina at the back of our eyes, it hits the
rods and
cones which respond to both light and color of the objects The rods and cones send signals to the option nerve that helps the brain to interpret the images we are seeing.
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| (c) M. Prince, 2012 |
The color that we see on the object is the color that is being
reflected. For instance, the eye images are focusing on a tree. We are able to see the green leaves and the brown trunk because The colors that make up green are being reflected while all other colors are being
absorbed. The same is said for the brown we see on the tree trunk.
How do we see the color on many objects?
The
electromagnetic spectrum is a wave with many frequencies. Remember the longer the wavelength, the lower the frequency. The shorter the
wavelength, the higher the
frequency. Now almost in the middle of the electromagnetic spectrum is a very small section of wavelengths that is just the right size for the
human eye to see. This section is called
visible light as previously stated.
Colors of Light vs. Colors of Pigments
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| http://www.diycalculator.com/imgs/console-09.gif |
Did you know that your eye can only detect three colors of light? Well, it's true. Your eye picks up red, green, and blue (see image above). Your brain helps you mix those three colors to get yellow, magenta, cyan, and of course, white. The colors that you see on the images in your television screen. Now every time you see a white image on the TV screen, you will know all the colors that help to make up that image's color.
Now while you may be able to mix all those colors to get white light, I highly do not recommend that you get your paint set and mix all those colors up to get white. It simply won't work! Pigment colors do not produce the same colors when mixed. In school, you have been told that your primary colors are red, blue, and yellow also, right? Well, that is not exactly true. The primary colors of pigment are yellow, cyan, and magenta. Magenta and yellow make up red, while magenta and cyan make up blue. When you mix all these colors together you get black, which is quite different from colors of light being combined.
This begs the question: How exactly can you create black from the colors of light? The answer to this is quite simple. In order to see black, it requires that absence of light. Think about it: If you remove all light-producing objects in your room, close your bedroom door and windows, the only thing you will see are black objects. Give it a try!
Here's a website that covers a great deal of information on
Light and Color.
Can you answer the questions for last week's post now?
1. What is the color of George Washington's white horse?
2. Why do you suppose we can only see black at night?
3. What is the difference between colors of light and colors of pigment?
4. How does light interact with different materials?
Making Waves Lab
It took the entire week to do this lab. I have some students who volunteered to share their discoveries and understandings from this lab. Be on the lookout for this upcoming student podcast!
I had a wonderful time sitting down with several groups this week to "listen in" on what they learned about the properties of waves and the relationship between speed, wavelength, and frequency.
Here are a few videos I created on measuring waves that you may find helpful. While doing this lab, we have to find the speed of the wave by calculating the distance of each wave (4m) by the time it took in each trial. Once we found the speed of each wave, we could then calculate for the frequency, by substituting what we already knew (speed and wavelength) and setting up our formula (frequency = wave speed / wavelength). The three videos show us how to generally solve for the unknown.
