Rainbows & Mirages
Israel Kamadawiwo's version of
Somewhere Over the Rainbow
Wizard of Oz's Somewhere Over a Rainbow
To understand rainbows, you must first understand dispersion.
Click here for a great diagram of dispersion
What causes a rainbow?
Here is a diagram of the primary rainbow to trace on your homework sheet
and here is a diagram of the secondary rainbow to trace next to the primary on your sheet.
Or put both the primary and secondary rainbows in the same diagram
Here is a great power point presentation on rainbows in just half of 13 minutes.
How do transition lenses work?
Photochromic lenses have millions of molecules of substances such as silver chloride or silver halide embedded in them. The molecules are transparent to visible light in the absence of UV light, which is normal for artificial lighting. But when exposed to UV rays, as in direct sunlight, the molecules undergo a chemical process that causes them to change shape. The new molecular structure absorbs portions of thevisible light, causing the lenses to darken. The number of molecules that change shape varies with the intensity of the UV rays.
When you go indoors and out of the UV light, a different chemical reaction takes place. The absence of the UV radiation causes the molecules to "snap back" to their original shape, resulting in the loss of their light absorbing properties. In both directions, the entire process happens very rapidly.
When you go indoors and out of the UV light, a different chemical reaction takes place. The absence of the UV radiation causes the molecules to "snap back" to their original shape, resulting in the loss of their light absorbing properties. In both directions, the entire process happens very rapidly.
Why is wet sand darker than dry sand?
For sand grains in water, the change in the direction of light is smaller than in air. The figure below illustrates the difference:-
click for diagram
It shows that, on average, it takes a much longer path for light in wet sand to come out (left) than in dry sand (right). The longer the path, the greater the chance that light gets absorbed. Hence, wet sand looks darker than dry sand
click for diagram
It shows that, on average, it takes a much longer path for light in wet sand to come out (left) than in dry sand (right). The longer the path, the greater the chance that light gets absorbed. Hence, wet sand looks darker than dry sand
