Investigating Light Properties: Physics Lab

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  • 0:01 What Are the…
  • 0:30 Physics Lab Steps
  • 3:00 Data Analysis
  • 4:13 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

After completing this lab, you will be able to list the properties of light and complete investigations that show some of these properties. A short quiz will follow.

What Are the Properties of Light?

Today we're going to investigate the properties of light. A property is an attribute, quality or description of something, usually in a way that can be quantified or compared. Light has many properties. Fundamentally, its properties are intensity (which is brightness), direction, frequency (which is color) and polarization. But we can investigate the properties of light more generally by seeing how it behaves in different circumstances.

Physics Lab Steps

For this physics lab, you will need:

  • A flat mirror and something to help stand it upright (like clips or clothespins or books)
  • A piece of paper and pencil
  • A ruler
  • A protractor
  • A straight pin or thumbtack
  • A laser pointer

Step 1: Take your piece of paper, fold it in half and then use the ruler to draw a line along the fold.

Step 2: Stand your mirror on top of the line. Make sure it's straight upright. (You can use document clips or clothespins or something else that's on hand to hold the mirror steady). Don't let the mirror move at all during the lab.

Step 3: Draw a large dot or cross on the paper, in front of the mirror, but towards one side of the paper (meaning, not right in the middle). Then stick a pin or thumbtack in the dot or cross. The longer the pin, the easier it will be to complete the lab. (A thumbtack is a bit short, though it's definitely usable).

Step 4: Lower yourself until you're looking right along the surface of the paper. Position your eye in front of the mirror, but at the opposite side to the pin.

Step 5: Use the ruler to draw a line from your eye, along the paper, to where the pin appears in the mirror. Do this carefully, as you would if you were playing pool, lining up a shot.

Step 6: Repeat step 5, but from a slightly different position on the paper; move your eye somewhere else. After this, you should have two lines on your paper, from the two different positions where your eye was, to where your eye saw the pin in the mirror.

Step 7: Remove the mirror and extend your two lines until they cross, using the ruler. Keep the lines solid on the side of the mirror where the pin was, but dash the lines on the opposite side of the mirror.

Step 8: Where the lines meet the mirror, connect them to the dot or cross you drew. Each of the two lines should meet the mirror and then 'bounce' off until they reach the dot or cross.

Step 9: Where the line bounces off the mirror, draw a line at 90 degrees (right angles) to the mirror surface. Use a protractor if you're not sure.

Step 10: Measure the angle between the line from your eye and the 90-degree dashed line, and note it down. Also measure the angle between the reflected (bounced) line and the 90-degree dashed line, and note it down.

Step 9: If you have a laser pointer, put the mirror back in position. Shine the laser along each of the lines you drew from your eye, right along the surface of the paper. You should find they bounce off the mirror, and follow the line you drew to meet the pin.

If you haven't already, now it's time to pause the video and get started. Good luck!

Data Analysis

Observations of Lab
diagram of lab

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