One of the best science fair project ideas for students that are particular interested in the science and mathematics of light travel is the Joly Photometer. This project allows students to use the inverse square law to measure light intensity. This may not be one of the best projects for students in lower grades, as the project requires an understanding of some difficult mathematic concepts.

In order to perform this experiment, students will need to spend between $ 20 and $ 50. The project should take about a week, which makes it one of the more time-consuming science fair project ideas that I've come across. Also, students might want to have a parent around to make sure the project is done safely.

**Objective:**

During this project, you will measure the light intensity of light bulbs using your own hand-crafted photometer.

**Introduction:**

Through this project, you will learn that different light sources have different powers to project light into a room. Every light bulb in your home may not have the same ability to emit light the same distance. During this project, you will learn about the basic differences between how light bulbs work. Plus, you'll build and use your very own photometer.

**Terms and Concepts You'll Need to Know:**

You'll learn much more about these terms and concepts through the course of your experiment, but it's a good idea to start with a basic knowledge of them:

- Inverse square law (you'll learn lots about this law!)
- Incandescent light bulbs (you may already have some in your home)
- Compact fluorescent light bulbs
- Photometer (you'll make your own)

**Questions You'll Answer:**

- What makes incandescent light bulbs work?
- Why do incandescent light bulbs die?
- What makes fluorescent light bulbs work?
- Why do fluorescent light bulbs die?
- Which is the longest lying light bulb?
- Which light bulb makes light most efficient?

**Materials You'll Need:**

You should not have to pay more than $ 50 for all of these materials, but you'll probably find most of them in your home already:

- One pound of paraffin wax
- A sharp knife
- Foil
- Cardboard box (small)
- Scissors
- Tape
- Identical light fixtures
- Measuring tape (not a ruler)
- Several kinds of light bulbs

**Procedure:**

Follow these steps in order to successfully complete one of the best science fair project ideas for determine how light works differently with different bulbs:

- Cut one slab of the wax in half. (Each box of wax should have four slabs).
- Cut aluminum foil to be the same size as the slabs and place it in between the 2 slabs.
- Create a cardboard box around the slabs. Use tape to hold it together.
- Make 3 windows in the sides of the cardboard box (one side will not have a window). This is your photometer.
- Place the photometer straight between 2 light fixtures at equal distances and equal heights. Make sure these light fixtures are the only sources of light in a room.
- With the light bulbs illuminated, move the photometer between the two light bulbs until the wax has the same level of brightness on each side of the aluminum foil.
- To find the inverse square law, use the standard equation, which is found here.
- One of your light bulbs should be your standard bulb. This bulb should be called I1. To find the intensity of the second light, make sure you divide the first light by the square of the distance and make it equal to the second light divided by the square of the distance so both lights are equidistant from the meter.
- Measure the distance from each light bulb to your photometer (measure to the foil).
- Use the equation to calculate the intensity of each bulb.
- In order to find out how efficient each bulb is, divide the relative intensity by the wattage of the bulb.

Again, this is one of my favorite science fair project ideas for students that enjoy math and physics. However, it can be tough for those students that do not quite understand tricky equations. Science projects should be fun – so have fun doing this project!

If you're ready to get going with your own light intensity science project, your next step is to download a free copy of "Easy Steps to Award-Winning Science Fair Projects" from the link below right now.