3/19/12
Only Tangentially Relevant
The Higgs Boson always occupies some portion of the science press... here's an explanation of it that I think works very well...
Bending That Light
Today was all about lenses and image formation and groups endured either the math involved with predicting image properties or using ray diagrams to analyze image formation by lenses.
B, E and F Blocks took their first steps with lenses today (well, E and F Blocks do have some lab experience in this area). The characteristics of converging and diverging lenses were examined and their abilities form images was explored. We spent time working through the construction of a ray diagram for a converging lens making a real image and folks have some more of these to do for homework. B and E Blocks also have a virtual image to deal with, so don't forget that you have a nice textbook to help you with that (might check page 571), but F Block only has to worry about real image formation. We'll look over these tomorrow before moving on to using the thin-lens formula and magnification formulas to more precisely hammer down numbers for image position and size.
C Block reviewed their ray diagrams and used those diagrams as examples to help clarify the relationship between object position and type/size of image formed for converging lenses. As you move the object towards the lens, the real image formed grows in size and moves away from the lens (q and M increase). At the focal point, the image forms at infinity and if you continue to push the object forward, the image now becomes virtual, with image distance and magnification increasing as you progressively approach the lens. We then started working on the math involved with lenses to put some precise values for our image properties and your homework tonight will give you additional practice working with the thin-lens and magnification formulas. We'll go over this and the 15.1 homework tomorrow before starting your lab on lenses.
B, E and F Blocks took their first steps with lenses today (well, E and F Blocks do have some lab experience in this area). The characteristics of converging and diverging lenses were examined and their abilities form images was explored. We spent time working through the construction of a ray diagram for a converging lens making a real image and folks have some more of these to do for homework. B and E Blocks also have a virtual image to deal with, so don't forget that you have a nice textbook to help you with that (might check page 571), but F Block only has to worry about real image formation. We'll look over these tomorrow before moving on to using the thin-lens formula and magnification formulas to more precisely hammer down numbers for image position and size.
C Block reviewed their ray diagrams and used those diagrams as examples to help clarify the relationship between object position and type/size of image formed for converging lenses. As you move the object towards the lens, the real image formed grows in size and moves away from the lens (q and M increase). At the focal point, the image forms at infinity and if you continue to push the object forward, the image now becomes virtual, with image distance and magnification increasing as you progressively approach the lens. We then started working on the math involved with lenses to put some precise values for our image properties and your homework tonight will give you additional practice working with the thin-lens and magnification formulas. We'll go over this and the 15.1 homework tomorrow before starting your lab on lenses.
3/16/12
Lenses
Some folks worked with lenses today, either in lecture or in lab, while others toodled through the basics of refraction.
B and F Blocks took time to get a general understanding of the phenomenon of refraction and how a material's index of refraction impacts the speed, wavelength and path of travel for a ray of light. We linked refraction and index of refraction to dispersion of light by prisms and relied on the law of refraction and Snell's Law to put some actual numbers to our general descriptions. On Monday, we'll move onto lenses, which F Block investigated yesterday and B Block will explore next Wednesday.
C Block started their work on lenses today. We defined what is and isn't a lens and investigated image formation by both converging and diverging lenses. With those ideas in mind, we moved to better describe image formation through the use of ray diagrams. Like I said in class, I wont' ask you to craft a ray diagram for a diverging lens or for a converging lens when it is making a virtual image. However, you should be able to draw one for a converging lens making a real image, as we practiced. Tonight's homework will let you start to examine the relationship between object placement and type, size and position of image and we'll throw the more precise calculations into the mix on Monday.
E Block worked on their Image Formation by Lenses lab, testing both converging and diverging lenses. The converging lens gave you nice, real images that you caught on a screen and let you form a virtual image that you had to look through the lens to see. The diverging lens only makes virtual images, but you could at least use the divergence of the rays from the laser pointer to back-calculate the focal length of the lens. We'll go over this lab on Monday before moving to a more in-depth treatment of lenses.
B and F Blocks took time to get a general understanding of the phenomenon of refraction and how a material's index of refraction impacts the speed, wavelength and path of travel for a ray of light. We linked refraction and index of refraction to dispersion of light by prisms and relied on the law of refraction and Snell's Law to put some actual numbers to our general descriptions. On Monday, we'll move onto lenses, which F Block investigated yesterday and B Block will explore next Wednesday.
C Block started their work on lenses today. We defined what is and isn't a lens and investigated image formation by both converging and diverging lenses. With those ideas in mind, we moved to better describe image formation through the use of ray diagrams. Like I said in class, I wont' ask you to craft a ray diagram for a diverging lens or for a converging lens when it is making a virtual image. However, you should be able to draw one for a converging lens making a real image, as we practiced. Tonight's homework will let you start to examine the relationship between object placement and type, size and position of image and we'll throw the more precise calculations into the mix on Monday.
E Block worked on their Image Formation by Lenses lab, testing both converging and diverging lenses. The converging lens gave you nice, real images that you caught on a screen and let you form a virtual image that you had to look through the lens to see. The diverging lens only makes virtual images, but you could at least use the divergence of the rays from the laser pointer to back-calculate the focal length of the lens. We'll go over this lab on Monday before moving to a more in-depth treatment of lenses.
3/15/12
Refraction for All!
Today began our journey through the world of refraction and lenses (aka Chapter 15). B Block had to go it alone since I was summoned to talk with parents of incoming freshmen for scheduling concerns, so they slogged through Snell's Law and the law of refraction on their own. Tomorrow, we'll add some explanation to all of that...
C and E Blocks discussed the phenomenon of refraction - the change of speed, direction and wavelength of light when it changes media - and how to quantify the speed and direction change. Be very clear about what happens when light enters a more denser material (slows down, shorter wavelength, path closer to normal line) and when it enters a less dense medium (faster speed, longer wavelength, path diverges from normal line). We looked at the property of transparent materials called the index of refraction and what that meant in terms of wave speed in that material. Lastly, we related the phenomenon of dispersion to refraction. In materials with a significant index of refraction like a diamond or quartz, there is a very noticeable difference in the speed changes and path of travels for the different colors of light. Tomorrow, apply refraction to yet another concept - image formation by lenses.
F Block worked on their lens lab during long block. Both converging and diverging lenses were investigated for patterns of image formation. As with converging mirrors, converging lenses can make real or virtual images dependent on placement of the object. Diverging lenses, like diverging mirrors, can only form virtual images smaller than the object. We'll dive into this topic in detail on Monday, but tomorrow is set aside to get a handle on refraction and how to evaluate the effects of refraction on the motion of light.
C and E Blocks discussed the phenomenon of refraction - the change of speed, direction and wavelength of light when it changes media - and how to quantify the speed and direction change. Be very clear about what happens when light enters a more denser material (slows down, shorter wavelength, path closer to normal line) and when it enters a less dense medium (faster speed, longer wavelength, path diverges from normal line). We looked at the property of transparent materials called the index of refraction and what that meant in terms of wave speed in that material. Lastly, we related the phenomenon of dispersion to refraction. In materials with a significant index of refraction like a diamond or quartz, there is a very noticeable difference in the speed changes and path of travels for the different colors of light. Tomorrow, apply refraction to yet another concept - image formation by lenses.
F Block worked on their lens lab during long block. Both converging and diverging lenses were investigated for patterns of image formation. As with converging mirrors, converging lenses can make real or virtual images dependent on placement of the object. Diverging lenses, like diverging mirrors, can only form virtual images smaller than the object. We'll dive into this topic in detail on Monday, but tomorrow is set aside to get a handle on refraction and how to evaluate the effects of refraction on the motion of light.
3/14/12
Test Day!
Everyone except the skippers endured their light and reflection tests and will start on refraction tomorrow. F Block will be working on a lab that lets them investigation formation of real and virtual images by lenses and the rest of the folks will be looking at the phenomenon of refraction and how to predict the direction of refracted light rays using Snell's Law. See you then!
3/13/12
Combo Post
Didn't a chance to post yesterday, but everyone knows what we did so who really cares? B Block worked on their light intensity and polarization lab, which we discussed in class today and reinforced the ideas that we went over in our class lectures. C, E and F Blocks took time to go over the ideas of color and polarization. We had already done lab work on polarization, so that concept flowed smoothly, but folks usually have a little trouble with the additive and subtractive color systems. Understanding the systems is not hard, but understanding what you would see when you mix colors of light or pigment or shine light on a colored object can be troublesome. We took time in class today to go over that homework and try and get everyone on board before we took our customary walk through the chapter material (also applies to B Block)in preparation for tomorrow's test. Remember your sign conventions for your mirror problems, forget about parabolic mirrors and make sure you can draw a ray diagram for real image formation by concave mirrors. I'm in before school tomorrow, so stop by if you need any last minute help. Starting on Thursday - refraction and lenses!
3/9/12
Phryday!
B Block took on the challenge of color and polarization today. We looked at the additive and subtractive color systems and looked at a few demonstrations to see how additive color works for televisions and computer screens and subtractive color systems work using a spectrophotometer. We then hit polarization and discussed how light could become polarized through passing through a filter, reflection or scattering. We also took time to look at how a polarizing filters could be used to block previously-polarized light and how that related to sunglasses and camera lenses. On Monday, a lab about light intensity and polarization.
C Block worked on their light intensity and polarization labs today and found, as expected, that the relationship between light intensity and distance is an inverse-square one. We spent enough time on that between sound and the first part of this chapter that it should be pretty easy to write the Conclusion part of your write-up for that piece of the lab. For polarization, you used one filter to polarize light and a second (the analyzer) to demonstrate how light penetration changes with angle of analyzer. The sunglasses lens showed the same pattern, so both nicely followed Malus's law, which we'll touch on in class Monday.
E and F Blocks discussed curved mirrors in class, both concave and convex, and how examined how these mirror types formed images. We contrasted real with virtual images, explained how to use the mirror equation and magnification formulas and looked at how to draw ray diagrams for these mirror types. Remember that you are only responsible for drawing ray diagrams for concave lenses forming real images, but be sure you can do that quite well for the test. On Monday, we take a look at color and polarization.
C Block worked on their light intensity and polarization labs today and found, as expected, that the relationship between light intensity and distance is an inverse-square one. We spent enough time on that between sound and the first part of this chapter that it should be pretty easy to write the Conclusion part of your write-up for that piece of the lab. For polarization, you used one filter to polarize light and a second (the analyzer) to demonstrate how light penetration changes with angle of analyzer. The sunglasses lens showed the same pattern, so both nicely followed Malus's law, which we'll touch on in class Monday.
E and F Blocks discussed curved mirrors in class, both concave and convex, and how examined how these mirror types formed images. We contrasted real with virtual images, explained how to use the mirror equation and magnification formulas and looked at how to draw ray diagrams for these mirror types. Remember that you are only responsible for drawing ray diagrams for concave lenses forming real images, but be sure you can do that quite well for the test. On Monday, we take a look at color and polarization.
3/8/12
Reflection
Today was a day of reflection - HAH!
B and C Blocks took up the topic of curved mirrors and image formation. We looked at how both mirror types create images, contrasted real and virtual images, worked with the mirror equation and the two magnification formulas and discussed the construction of ray diagrams. Remember that I won't ask you to draw a ray diagram for a virtual image on a test, but I will ask you to do one for a real image and use the appropriate formulas for any type of image formation. Tomorrow, C Block works on their light intensity and polarization lab and B Block moves on to color and polarization.
E and F Blocks talked about reflection and image formation by plane mirrors. We contrasted specular and diffuse reflection and showed how the law of reflection accounted for both reflection types. We then turned attention to plane mirrors and how/why the formed their particular type of image. Remember that plane mirrors form virtual, upright images the same size and distance from the mirror as the object. Tomorrow, we'll complicate things by taking up the challenge of curved mirrors.
B and C Blocks took up the topic of curved mirrors and image formation. We looked at how both mirror types create images, contrasted real and virtual images, worked with the mirror equation and the two magnification formulas and discussed the construction of ray diagrams. Remember that I won't ask you to draw a ray diagram for a virtual image on a test, but I will ask you to do one for a real image and use the appropriate formulas for any type of image formation. Tomorrow, C Block works on their light intensity and polarization lab and B Block moves on to color and polarization.
E and F Blocks talked about reflection and image formation by plane mirrors. We contrasted specular and diffuse reflection and showed how the law of reflection accounted for both reflection types. We then turned attention to plane mirrors and how/why the formed their particular type of image. Remember that plane mirrors form virtual, upright images the same size and distance from the mirror as the object. Tomorrow, we'll complicate things by taking up the challenge of curved mirrors.
3/7/12
John Carter
There is a lot of negative buzz about the upcoming Disney film - John Carter- and that bums me out. Growing up, Edgar Rice Burroughs books held a very prominent position on my bookshelf. His Mars books were great - lots of sci-fi and loads of action - who could ask for more? I have no idea what the movie version is going to be like, but the first book in the series - A Princess of Mars - is a killer read. You can read it for free (legally) from Project Gutenberg, where you can find more of the Mars books and his Tarzan books, too (Edgar Rice Burroughs at Project Gutenberg).Do yourself a favor and read some of those classic sci-fi authors... you'll be glad you did.
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