Hands On Physics

Messing Around

More of the Story: Initial Investigations

Pollution of light sources (most notably the sun) are of some concern as we look into the future and think that nuclear war or continued use of combustion engines or industries or even natural disasters like volcanic eruptions might BLOCK the wonderful sunlight we now enjoy and "take for granted". Notice how one hardly ever wonders whether the next day is going to have light instead of dark. One hardly ever wonders whether night will continue through the next day except perhaps our colleagues closer to the North or South poles where weeks of sunlight or darkness exists. Some who work and study in polluted areas are very aware of the pollution because it tends to partially block the sun.
It is the bad air that rises and gets to the upper reaches of the troposphere (that layer of air where we live and breathe). Sunlight is partially blocked but such pollution. We call the phenomena - haze.


We are attempting to eventually find out the amount of haze in our local area and to record this data at regular intervals to provide a much needed database for students and scientists around the world.

To study haze, you need to know about light. We are concerned here with some of the properties of light as we consider haze and light pollution.


You will be determining the amount of haze in the air by measuring light intensity. What problems arise when measuring light intensity, and how can you eliminate these problems? These are some of the questions about light that you will need to answer before you start to study haze.


The first thing you do in a HOP unit is "messing around". This part of the unit gives you a chance to gain an understanding of the basic ideas without having to worry about running detailed experiments. This can be fun, but still quite serious. Keep your eyes open, ask lots of questions, and write down your observations. You should always be asking yourself
There are four investigations in this section. You explore how light is spread out (scattered) when it shines past small particles, and you investigate several light souces and several detectors of light. You build some electronics for detecting light, and you study color .

Investigation 1: Scattering.

Investigation 2: A Light Detector.

Investigation 3: Signal Amplifier.

Investigation 4: The Spectrum.

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