Objectives:
While exploring this page, the web-surfer/student will be able to:
1. Learn the basic concept of wave-partical duality
2. Understand and solve for frequency and wavelength in situations involving the electromagnetic spectrum
3. Learn about the applications of the knowledge of wave-partical duality
 

Basic Concepts:
 

LIGHT IS A WAVE
 

    All waves have:
        Frequency: visible light frequencies range from 4 x 10^14 Hz to 7.9 x 10^14 Hz
            - frequency is measured in Hertz (Hz)
            -to solve for frequency we use the equation f = c/l where c = speed of light and l = wavelength
        Velocity: the speed of light in a vacuum is 3.0 x 10^8 m/s
            - this value is often represented in equations as "c"

courtesy http://phys.udallas.edu/C3P/cartoons.html

    Example problems:
        1. Find the wavelength of a light wave with a frequency of 6 x 10^14 Hz

        2.  Find the frequency of a wave of light with a wavelength of 740 nm

        3.  What is the wavelength of a light wave with frequency 7.9 x 10^14 Hz?  What color is this light?

    Properties of waves:  Waves can
        Refract: (like in a prism)
        Reflect: (like in a mirror)
        Diffract: (through a keyhole)

    How do we use light's wave properties?
        1.  Light is refracted through lenses in eyeglasses and magnifying glasses
        2.  Light is reflected off of mirrors for personal use and in vehicles for safety
        3.  Light is reflected and refracted so we can see images through microscopes and telescopes.
        4.  CD players shine a laser onto the CD, which has raised and lowered areas around a spiral track.  The laser light is reflected and read by the CD player, which interprets it and produces the sounds we hear.
        5. Our own eyes are equipped with lenses through which light enters.
 
 
 

LIGHT IS A PARTICLE
 
 

    What???  Light is a particle?  Light... has mass?  Light weighs something?  Yup.  If you don't quite understand that, don't worry.  The brightest minds in the world didn't figure this one out until the early 20th century.  But it's true, and the knowledge has helped us in several ways.

    Okay, follow the logic here for a second.  Light is a particle.  Particles have mass.  Light has mass.  Light moves (we know this because it's a wave, and waves have velocity).  Anything that has mass and velocity has... yes, that's right -- mass x velocity = momentum!  And as you know if you've ever been in bumper cars, anything that has momentum can cause a collision.  Collisions are the transmission of energy.  Sometimes that energy is manifested in causing  movement.  So light can move things.  It can't normally move very big things, mind you, but it still has the capacity to cause things to move.  Scientists discovered that light can collide with small things, such as electrons, and cause them to move.  And what is the movement of electrons?  Electricity!  So light can create electricity!  That's what active solar cells do.  Light hits particles on the solar cell and causes collisions which cause energy to be transmitted in the form of electricity. Solar power is a form of energy that will increase in importance as we search for clean, environmentally-sound ways to generate electricity.  And it's all because light is both a wave and a particle.