slideText.html

<section class='hidden'>
    <section class='chapter' id="slide1">
        <p>
            We begin by learning a little about the properties of light. We 
            will use 
            visual models like the one shown to the right to represent 
            a laser beam. 
        </p>
        <p>  
            Light carries <em>energy</em> and this
        energy comes in discrete packets called photons.  The number carried
        in even a fairly weak beam, as in a small laser pointer, is truly stupendous.
        Put your hand in a weak laser beam with about a milliwatt of power 
        and a every second about 
        1,000,000,000,000 (a thousand trillion) 
        photons will be hitting it.
        </p>
        <p>
            Click the button below to visualize the photons.
        </p>
        <p> 
            In a real laser, the photons move at the speed of light.
            We've slowed them down by a factor of about a trillion here.  With
            the <a href="https://en.wikipedia.org/wiki/Single-photon_avalanche_diode">
            right kind of detector</a>, and a weak enough beam, you can actually
            hear a click every time a photon is absorbed.
        </p>
        <p>
            When you are ready to continue hit the forward arrow.
        </p>
    </section>
    <section class='chapter' id="slide2">
        <p>
            Light also carries <em>momentum</em>.  With every photon absorbed 
            a target will feel a little kick. Each photon only provides the
            tiniest of kicks, but added together, and over time a beam of light can
            exhert enough force to get objects to move.  This force is often called 
            <em>radiation pressure</em>.
        </p>
        <p>
            One of the more exciting proposals for sending a ship to 
            a nearby star system would use radiation pressure to push tiny satelites
            up to enormous speeds.  The satelites would deploy a 
            <a href="https://en.wikipedia.org/wiki/Solar_sail">solar 
            sail</a> to catch the light.
        </p>
    </section>
    <section class='chapter' id="slide3">
        <p>
            It takes a lot of laser power to move an everyday object,
            but a single atom can be pushed around quite easily.  With the laser
            from a hand held laser pointer alone you could cause an atom to
            accelerate at rate 10<sup>4</sup> times faster (10<sup>4</sup> <em>g</em>'s) 
            than we do at earth's surface. That's fast!
        </p>
        <p>
            Here's our laser again.  Push the button a few times to release some
            atoms and watch them drift into the beam.  You'll see them pushed
            in the direction the laser is pointing.
        </p>
        <p>

        </p>

    </section>
</section>