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Spring 2006. UCSD: Physics 8; 2006. 2. What do we see?. Our eyes can\'t distinguish inborn light from articles (generally infrared), unless they get
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Light Color Addition & Subtraction Spectra

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UCSD: Physics 8; 2006 What do we see? Our eyes can\'t recognize natural light from articles (for the most part infrared), unless they get " intensely hot " The light we see is from the sun or from counterfeit light When we see objects, we see reflected light quick ricocheting of occurrence light (zero postponement) Very sporadically we see light that has been consumed, then re-discharged at an alternate wavelength called fluorescence, glow, radiance

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UCSD: Physics 8; 2006 Colors Light is described by recurrence, or all the more regularly, by wavelength Visible light traverses from 400 nm to 700 nm or 0.4 m to 0.7 m; 0.0004 mm to 0.0007 mm, and so forth

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UCSD: Physics 8; 2006 White light White light is the mix of all wavelengths, with equivalent representation " super hot " poker has a great deal more red than blue light test: red , green , and blue lights make white R G B screen consolidates these hues to show white joined, white light called added substance shading blend — works with light sources wavelength red light green light blue light

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UCSD: Physics 8; 2006 Additive Colors Red , Green , and Blue light sources can be utilized to integrate any discernible shading Red + Green = Yellow Red + Blue = Magenta Green + Blue = Cyan These three double source hues turn into the essential hues for subtraction why? since nonappearance of green is maroon nonattendance of red is cyan , and so on

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UCSD: Physics 8; 2006 reflected yellow light (blue gone) episode white light blue ingestion (e.g., paint, color) yellow light made of red and green Subtractive hues But most things we see are not light sources Reflection takes away a portion of the occurrence light along these lines the term subtractive If episode light is white, yellow is nonappearance of blue

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UCSD: Physics 8; 2006 What\'s in charge of specific retention? Carotene makes carrots orange , tomatoes red , daffodils yellow , leaves turn must ingest blue light Long, natural atomic chain most colors, shades are such resonances in optical light Chlorophyll makes leaves green must ingest red and blue

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UCSD: Physics 8; 2006 Questions Why, when you combine every one of your paints, do you simply get dull cocoa or dark ? Why not white? Why is the sky blue , and the low sun/moon orange ? Are these related?

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UCSD: Physics 8; 2006 Our constrained affectability to light In brilliant light circumstances (called photopic , utilizing cones), our affectability tops around 550 nm, going from 400 to 700 oblivious, we change to scotopic vision (bars), focused at 510 nm, going from 370 to 630 it\'s the reason cosmologists like red electric lamps: don\'t destroy night vision

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UCSD: Physics 8; 2006 Introduction to Spectra We can make a range out of light, analyzing its constituent hues A crystal is one approach to do this A diffraction grinding likewise does the employment The range speaks to the wavelength-by-wavelength substance of light can speak to this in a shading realistic like that above or can plot force versus wavelength past plots of blackbody range were of this structure

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UCSD: Physics 8; 2006 Example Spectra white light range hydrogen light range helium light range lithium light range mercury light range hydrogen assimilation range Spectra give "fingerprints" of nuclear species, which can be utilized to recognize molecules over the universe! Sun based Spectrum with Fraunhofer sun based climate assimilation lines C: Hydrogen; D: Sodium; E: Iron; F: Hydrogen; G: Iron; H&K: Calcium

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UCSD: Physics 8; 2006 Spectral Content of Light A range is a plot speaking to light substance on a wavelength-by-wavelength premise the heap hues we can see are basically distinctive phantom amalgams of light much like diverse instruments have distinctive sound: it relies on upon its (symphonious) ghostly substance

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UCSD: Physics 8; 2006 Light Sources Here are an assortment of light sources. Included are: H-ITT IR LED * red LED * green laser pointer flourescence of orange H-ITT trans-mitter lit up by green laser Note that light must be blue-ward (shorter wavelength) of the fluorescence for it to work. * LED: Light Emitting Diode

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UCSD: Physics 8; 2006 Colored Paper Reflected light (for this situation, daylight) off of paper showing up: blue green yellow orange red dark beside slight fluorescence in yellow paper, paper hues work by reflection just : never looks above 100% white paper would be a level line at 100%

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UCSD: Physics 8; 2006 Fluorescent Paper Bright fluorescent paper takes after various principles: retains blue or UV light and re-discharges at some trademark wavelength. These cases are of lime green paper and splendid orange fluorescent paper. Note particularly in the orange case, the light surpasses the sum that would be inactively reflected off of white paper (100% level)

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UCSD: Physics 8; 2006 Fluorescent Markers (hello there lighters) Likewise, fluorescent markers (howdy lighters) ingest and re-transmit light. For this situation, we see yellow , green , and pink fluorescent markers The pink really has a touch of blue/violet in it, shockingly All three have discharge over the 100% that one gets from straight reflection

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UCSD: Physics 8; 2006 Fluorescent lights Fluorescent lights invigorate outflow among particles like argon, mercury, neon they do this by ionizing the gas with high voltage as electrons recombine with particles, they radiate light at discrete wavelengths, or lines Mercury puts out a solid line at 254 nm (UV) this and different lines hit the phosphor covering within the tube and animate emanation in the unmistakable part of the range

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UCSD: Physics 8; 2006 LCD Monitor LCD screens use bright lights to enlighten the pixels (from behind). The dark bend demonstrates what my LCD portable workstation screen looks like in a segment of the screen that is white. Blue, green , and red bends show segments of the screen with these hues Note that the hues are accomplished essentially by concealment Green gets every one of this line Red gets every one of this line Blue gets every one of this line Thus LCDs simply channel the foundation light

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UCSD: Physics 8; 2006 Transmission of Glass, Sunglasses By acquiring a range of daylight reflected off of a bit of white paper (utilizing the spectrograph without the fiber sustain), then doing likewise through the fiber furthermore through shades , the trans-mission properties of each can be illustrated. The fiber is around 82% transmission for most wavelengths, however has noteworthy UV assimilation. This is the reason you can\'t get sunburn through glass The shades piece UV completely!

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UCSD: Physics 8; 2006 Sunlight and The Blue Sky These plots demonstrate the spectrograph\'s reaction to daylight on white paper and to the blue sky . The spectrograph is not exceptionally effective in UV or IR , and its affectability bend is appeared in dark . You can see the violet mound in the blue sky (brighter than white paper here). Likewise, can see the sunlight based climate ingestion lines in both sun and sky sodium hydrogen calcium oxygen in earth atmos. hydrogen

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UCSD: Physics 8; 2006 Blackbody amended The spectrograph programming gives you a chance to guarantee a source to be a dark group of determined temp-erature, so it can adjust for its effectiveness bend ( dark bend on prev.). Here we see the aftereffect of this procedure, which has made the sun bend resemble an immaculate blackbody topping at 500 nm. Yet, it additionally accepted that Fraunhoffer lines were ancient rarities to be expelled Note the sensational ascent of the sky toward the blue/UV end. The lighter blue is without the UV - engrossing fiber set up

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UCSD: Physics 8; 2006 More reasonable range Correcting the crude spectra from two slides back with the reaction bend , we land at a more practical sun and sky range. The dark line is a dark body at 5900 K, which fits the sun sensibly well. This time, the assimilation lines survive. The blue sky now likewise looks smoother, and on top of this is plotted a hypothetical 1/ 4 model for sub-atomic disseminating Though not in words, this clarifies why the sky is blue !

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UCSD: Physics 8; 2006 How do diffraction gratings work? A diffraction grinding is a standard cluster of optical scrambling focuses circular wave rises up out of every diffusing point helpfully or dangerously meddle at various edges relying upon wavelength

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UCSD: Physics 8; 2006 Another take a gander at diffraction gratings For a given wavelength, a unique edge will bring about useful obstruction: d  sin  =  this edge is diverse for various wavelengths

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UCSD: Physics 8; 2006 Assignments HW 7: 14.E.8, 14.E.19, 14.E.20, 14.E.21, 15.E.26 or more extra required issues on site, open through Assignments join Read pp. 446–447, 454–455 to go with this address Read pp. 447–453 for Thursday, 6/1 Extra Credit posted on course site worth up to 3% of evaluation!!! for the most part includes building a spectrometer and investigating heaps of things with it

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