Alta II Spectrometer


Each kit comes with 8 Alta II Reflectance Spectrometers. Included with the Alta II's is a booklet explaining their use and a number of ready made lab activities. These can serve as a great jumping off point for your classroom investigations, but you'll probably not want to do all of them. 

Basically, the Alta II will allow you to quantify the color of an object. Objects are the color that they reflect. So, a red ball is red not because it absorbs red light but because it reflects it. Other wavelengths (colors) of light are absorbed. The Alta II allows for the measurement of seven colors (wavelengths) of light in the visible spectrum as well as four in the near infrared. 

Things to Know:
  • Numbers on the screen vary from 0-1999. These are relative numbers, which means there are no units associated with them. The book includes directions for creating a calibration to use to convert the numbers into percent of light reflected.
  • It is way to easy to turn these on. I suspect this is why the instruction booklet recommends removing the battery prior to storage. If you store these with the battery in you should check them all to insure they are turned off.
  • The meter is reading all the time. In order to read the reflectance of a specific wavelength of light you put the spectrometer on the object and press and hold the wavelength you wish to measure. Pressing the button turns on an LED of the appropriate wavelength. The spectrometer should be blocking all the other ambient light so, the only light to reflect is the light you're interested in.
Possible Activities:
  • General Introduction - You should give students a chance to play with these as well as learn how to calibrate them.
  • Soil Moisture Content - If two things look different then they reflect light differently. You can tell wet from dry soil by sight so you should be able to quantify that. One of the activities from the guide walks students through using the Alta II to determine moisture content in soil. This is an activity I plan on fleshing out and probably re-writing to make it more inquiry based.
  • Ground Truthing - You can collect plants from your study area and collect data on reflectance to use with your ariel photography.
  • Nutrients? - It may be possible to determine the level of particular nutrients from the reflectance data. This would be a more involved experiment as students would first have to grow plants with known nutrient levels to create a scale.