Rainbow is an optical phenomenon in meteorology. When sunlight shines on water droplets in the air, the light is refracted and reflected, forming an arched colorful spectrum in the sky, which is red, orange, yellow, green, blue, indigo and purple from the outer ring to the inner ring. The following is the principle of rainbow after rain. Welcome to read it.
Why do rainbows appear after rain?
Rainbows are caused by the dispersion and reflection of small spherical water droplets when sunlight shines into the air. When sunlight enters the water drop, it will be incident at different angles at the same time and reflected at different angles in the water drop. Among them, the reflection of 40 to 42 degrees is the strongest, resulting in the rainbow we see. When this reflection is caused, the sunlight enters the water drop, first refracts once, then reflects on the back of the water drop, and finally refracts again when leaving the water drop. In total, it passes through one reflection and two refractions.
Principle of rainbow formation
Because water has a dispersive effect on light, the refractive index of light with different wavelengths is different. The refractive index of red light is smaller than that of blue light, and the deflection angle of blue light is larger than that of red light. Because the light is reflected in the water drop, the spectrum seen by the observer is inverted, with red light at the top and other colors at the bottom. Therefore, the height of rainbow and neon is different, and the layer order of color is just the opposite. Rainbow means that light is refracted twice and reflected once, while neon means that light is refracted twice and reflected twice.