How fast does light travel, and does it travel faster in water or air? The fastest thing in the whole universe is the speed of light in a vacuum (like outer space!), clocking in at a an excellent 2.99 x 108 m/s. Light travels in waves, and we call this travel propagation. Propagation of waves has both a speed and a direction, called the velocity. The velocity the light changes depends on the product it travel through.

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Light waves deserve to be readjusted in a couple of different ways. Reflection is when the waves bounce off a surface ar and readjust direction, like when they fight a mirror or swimming pool of water. Diffraction spreads the end light waves; an example of this is water vapor in the waiting diffracting light from the sun to develop a rainbow. The third type of light actions is refraction. Refraction is where light waves pass with a material (what scientists call a medium) and readjust direction. Have actually you ever stuck your arm beneath the surface ar of the water in a fractional or swimming pool, and also wondered why the looks like it has actually a sharp bend in it best at the surface? This is since of refraction!

In this project, friend will use a laser to measure refraction through various media. Laser is an acronym because that “Light Amplification by engendered Emission of Radiation,” i m sorry in basic terms method you space firing beams of irradiate in a straight line.


How does light refract in different ways when traveling through various media?


Sheets of paperPencilColored markerRulerProtractorCalculatorRectangular transparent material at least ¼” thick. Some examples include:GlassPlexiglassPlasticGelatinGlass dish filled with waterClear plastic food filled through waterLaser pointer or laser pen


Fold a clean paper of record in half.Place among the test materials on the folded paper of record so the centerline that the object is ~ above the fold.Trace the synopsis of the object onto the paper with the pencil.Use a colored marker to make a small dot ~ above the leaf of the sheet. This is where you will certainly aim the laser. This dot have to be top top the exact same side as the fold, at least 1.5 inches indigenous the fold. Why must the place where the laser will certainly be aimed it is in marked?Lay the laser under on the table or countertop and adjust the beam so that enters the page at the colored period you made and hits the thing at the centerline fold.


Turn the lights turn off if it makes it less complicated to watch the laser beam.Mark the laser beam route in and also out the the object with a few dots making use of the pencil.Use the protractor to measure up the angle of incidence and angle that refraction. Record the data and be certain to include any kind of observations. The edge of incidence (θ1) is the angular distance from a recommendation (in this instance the centerline fold) in ~ which the laser beam approaches and also hits the object. In this case, the tool is air. The angle of refraction (θ2) is the angular distance from a reference (in this case, the centerline fold) that light travels through the brand-new medium:


Using Snell’s law, calculation the rate of irradiate in the air and also in the test material. Snell’s law:

Repeat with various materials and compare the results.


Light will have actually the faster velocity when it travels through the air. Light will have the slowest velocity when it travels through gelatin.


Light slows down as soon as passing through different transparent materials. The much more it slow down, the more it bends when it access time a medium made of the material. Snell’s regulation of Refraction mirrors the relationship between incidence and refraction angles and also the phase velocities that the products involved. Because that this experiment, her laser beam traveled through an waiting phase prior to hitting the phase of every little thing solid friend chose. Snell’s legislation states the the proportion of the sine that the incidence come the refraction angles, θ, is same to the ratio of the step velocities, v.

Another variation on Snell’s law contains the index of refraction, n. The previously declared Snell’s law is same to the reciprocal of the ratio of the exponentiation of refraction.


The table of contents of refraction is a dimensionless number, or a number without any kind of units. Dimensionless number are used to have the ability to compare two various objects top top the same parameters. The table of contents of refraction define how light travels with a medium.

Where c is the speed of irradiate in a vacuum (2.99 x 108 m/s) and also v is the rate of light in the medium you are measuring in m/s.

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Going Further

Try adding salt or sugar to the water in the container and also perform the experiment again. What happens? Is the velocity different when friend dissolve solids in the liquid? You have the right to also shot measuring other see-through liquids favor clear soda or fluid soap. You have the right to also shot using various shaped objects like prisms come see exactly how light is refracted differently.

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