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    Selective transmission/absorption of light based on amplitude?

    As Naty1 linked above saturable absorption works in a similar fashion to what you proposed. When light intensity is high enough, there aren't enough electrons left in the ground state(due to finite upper state lifetimes) to absorb incoming photons. Subsequently, transmission increases until...
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    Violet light produced from green He-Ne laser?

    If you have a spectrometer you could see what wavelength it is you're looking at and try to associate an emission line with it. I remember seeing a similar spectra/color when building a He-Ne laser sans enclosure on an optical bench. Remember that the light coming from the He-Ne is green...
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    Magnetic shielding

    Why would silver be better than iron or" [Broken]? Not only is silver very expensive, but it's magnetic permeability is low comparatively. If the frequencies you are trying to block are high enough then you can move to a Faraday Cage, but for low frequency...
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    Charger could be there connected to mains all the time

    If it was as simple as putting the voltage from the wall across the battery of your phone your reasoning would be correct. However, a phone charger has components in between the wall and the phone to condition the signal so it's usable to charge the phone. None of these components are perfectly...
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    How do I asses the % of light transmission that passes through glass

    The easiest/fastest way to completely characterize the glass in the way that ZaperZ is talking about is to use a spectrometer. There are a lot of cheap (relative of course, ~3kish) compact prism spectrometers that do an amazing job of this. The one i use all the time is an Ocean Optics HR-4000...
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    Mirages on road

    Woops, was in the process of editing my post above to make it more clear. Post again if you still have questions.
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    Mirages on road

    Probably because you're seeing a reflection of the blue sky. As you said the reason that you actually see the sky/horizon/whatever is that the air near the hot black road heats up and acts as a mirror. As air heats up the index of refraction changes. A gradient temperature near the road produces...
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    Laser Induced Breakdown Spectroscopy

    Maybe it's oxygen in the atmosphere is reabsorbing those photons? It would depend on the flux coming from your sample and the distance to and sensitivity of your spectrometer set up. There might be a more obvious reason, I'm no spectroscopist.
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    Urgent - fiber optics illumination system

    As far as delivering/accepting the light: The amount of light a fiber can collect is based on it's Numerical Aperture (NA). The math for this is based on a index of refraction of the core and a cladding that the fiber is made of. Basically the NA tells you which light will enter and stay in...
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    Traveling 60mph, is it really 88 feet/second?

    I figured it was about right but instead of multiplying it out i got lazy and used alpha like i do more and more these days. I have a hard time grasping what feels right at pretty much any speed :P But then again i run pretty slow...
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    Light seems to bend around objects but why?

    I believe this is diffraction not refraction. Refraction is the bending of light when it enters a medium with a different index of refraction, ie light entering water. This is why fish look like they are in one spot but are actually in another. Diffraction is the bending of light as is...
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    Intensity of LEDs

    For a simple resistor only circuit V=IR absolutely does hold true. Sure, things will heat up and the resistance will change but ohm's law still applies it's just that a new value for R must be used. Also, generally as metals heat up they become more resistive but as semiconductors heat up they...
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    Hydrogen Is Positive

    Is it possible that your teacher was talking about a molecule of water? H2O is a polar molecule and the positive side will be towards the hydrogen atoms.
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    Journal Access, etc.

    Having recently lost access to my old universities online library and thus access to all of the journals that the college is subscribed to i am now seeking other means of accessing recent papers. Doing a bit of searching didn't turn up much unfortunately and as such i started thinking of what...
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    Worst Conductor Metal

    What f95toli said. For good hard insulators ceramics are great. Pretty much all we use in high vacuum environments. Teflon coated wires work great too but can't be heated like ceramics can. Also fired alumina is extremely hard and i've never actually broken or sheared a piece. I first...
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    Worst Conductor Metal

    Are you just looking for something to be used as a heating element? Then definitely just go with nichrome wire. Mainly nickel but with a large amount of chromium (15ish%). It's what i've used in the past to heat things up, but you need a pretty good power supply that can put out quite a bit of...
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    Laser in outer space

    Your assumptions are correct for an ideal laser. Unfortunately all lasers have a divergence angle that is dependent on both the wavelength and the inverse of the beam diameter at it's smallest spot. That is a blue laser with higher energy will diverge slower than a red one, etc.
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    Feynman Messenger Lectures (via Microsoft)

    Was just going to post this :) Yay for Feynman.
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    Introduction to optics

    I agree with mgb_phys' choice. Hecht is a good introduction to optics. I also own Fundamentals of Photonics by Saleh and Teich but preferred Hecht.
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    Engineering Electrical engineering opportunities?

    I just graduated from OIT (Klamath Falls, OR) with a degree in EET. I ended up going to graduate school for optical physics but the rest of my class that did not go to graduate school all ended up with jobs within 6 months and i believe that all but 1 of them are in the state of Oregon still. I...
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    Eliminating noise from Excel Data

    I'm a complete astronomy noob so if some of this is completely obvious just tell me to go sit in the corner:) Sooo..... Why you want to get rid of the hump in the first place? If your signal is almost the exact same everyday then why not just make comparisons between the day to day radio...
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    Laser safety

    This webpage has plenty of information on laser diodes. There is even an entire list of schematics for diode drivers if you want to build one of your own.
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    Why does it take more energy to heat nitrogen?

    If i understand this correctly the aluminum chamber is what's being heated which in turn heats the gas. The pressure in the chamber was stated to be 150-250 psi, so there is quite a bit of gas in the the chamber. That's 10-17 atmospheres of pressure. So while most of the aluminum will be giving...
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    What is voltage?

    As long as the field is a constant, yes.
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    What is voltage?

    There can absolutely be a voltage without a current. One example of this is simply an open circuit, ie a battery that's not hooked up to anything. Another way to think about it is this experiment. A way to measure the energy of an electrons ejected from a sample is to put a voltage from the...
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    SCENAR technology - frequency help please

    The "impulse" function (not really an impulse ie. dirac delta) can be described by a decaying sine wave. That is a sine wave that quickly dies off and repeats at frequency F. Where \omega =2\pi F Basically: Asin\omega*e^{-t/\tau} where A is the maximum amplitude of the voltage...
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    Difference between plano-convex and biconvex lens

    It won't matter at all. For a set up like a simple telescope all that matters are the focal lengths of the lenses. There shouldn't be much of a difference at all.
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    Cell phones and television.

    This also happens to me. A few seconds before my phone rings i'll get an audible hiss from my stereo if my phone is near enough to it. I can only assume that the cell phone is inducing noise in the stereo. It must be from the cell phone and not from the tower as it doesn't happen unless the cell...
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    Light reflection and color

    I'm a little confused by your definitions of warm/cool light... they don't make sense. Generally warm/cool have to deal with the temperature of the ball which really won't have anything to do with the color of the ball under any normal circumstances. So what you're really asking about is the...
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    Diffraction of Waves through a circular aperture

    What you're looking for is also known as the Airy Diffraction pattern.