To Measure the Refraction of Light through Liquids Using Crystals

Difficulty of Project (Easy, Medium, Hard)

Easy

Grade Level (Elementary, Middle, High School)

Upper elementary (grade 5) and/or Middle school (6-8)

Cost

$18.00 - Excluding the Tri-fold cardboard display board

Material Availability

Yes

Approximate Time Required to Complete the Project (hours, days, weeks)

One day once the materials are secured.

Objective

What is the project about?

The research aspect of this science fair project is to test various liquid substances using a Disappearing (hydro-gel) crystal to determine which, if any has the same Index of Refraction as distilled water.

What are the goals?

To develop a qualitative "index of refraction" like table, by placing disappearing crystals into water, cooking oil, rubbing alcohol, vinegar, even carbonated soda and recording the results as to the degree of "visibility" in the liquids to that of a distilled water control. The data will also be displayed as a bar graph of "crystal visibility" vs. liquid medium.

Materials and Equipment / Ingredients

What materials are required?

Disappearing (or hydro-gel) crystals, clear plastic cups, distilled water, string, cooking oil, rubbing alcohol, white vinegar, and club soda. With exception of the crystals, all the other items can be purchased from the local supermarket or drug store. Also, a Tri-fold cardboard display board can be purchased from an art & crafts supply store.

Where can the materials be found?

Introduction

Background information

Refraction is the bending of light waves caused by a change in their speed. The amount of bending that occurs depends on the speed of light in both materials. The greater the difference between the speeds of light in two media, the more the light is bent as it passes at an angle from one medium to another. A Disappearing Crystal (sometimes called a "hydro-gel crystal") when placed in water swells into a transparent tapioca-like bubble of encapsulated water. The crystal is made up almost entirely of water. The reason the crystal disappears when placed in water is because the crystal refracts the light the same as water and therefore cannot be seen while in the water. When the crystal is lifted out of the water and into the air, it becomes visible because the air's index of refection is very different then that of the water.

Substances can be grouped by their ability to bend light. This grouping is called the Index of Refraction. The research aspect of this science fair project is to test various common liquid substances to determine which, if any has the same index of refraction as distilled water.

Based on the amount of light refracted the investigator will develop a qualitative "index of refraction" table by placing disappearing crystals into various clear liquid substances (vinegar, cooking oil, rubbing alcohol, club soda, etc). He/she will record the results as the degree of crystal "visibility" in the liquids to that of the distilled water control. The data will be displayed as a bar graph of "crystal visibility" vs. Name of liquid medium.

Diagrams or Pictures

Digital photos can be taken during the experimenting process and/or images of crystals submerged in water can be downloaded from the Science in a bag website for free and without copyright infringement issues.

The following sites offer down loadable images that can be used on the display board: