Red is the color at the end of the spectrum of visible light next to orange and opposite violet. Red color has a predominant light wavelength of roughly 620–740 nanometres. Red is one of the additive primary colors of visible light, along with green and blue, which in Red Green Blue (RGB) color systems are combined to create all the colors on a computer monitor or television screen. Red is also one of the subtractive primary colors, along with yellow and blue, of the RYB color space and traditional color wheel used by painters and artists. 

In nature, the red color of blood comes from hemoglobin, the iron-containing protein found in the red blood cells of all vertebrates. The red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide. It also causes the red color of the planet Mars. The red sky at sunset and sunrise is caused by an optical effect known as Rayleigh scattering, which, when the sun is low or below the horizon, increases the red-wavelength light that reaches the eye. The color of autumn leaves is caused by pigments called anthocyanins, which are produced towards the end of summer, when the green chlorophyll is no longer produced. One to two percent of the human population has red hair; the color is produced by high levels of the reddish pigment pheomelanin (which also accounts for the red color of the lips) and relatively low levels of the dark pigment eumelanin. QUESTIONS:

Q1:
1. What shade is red's opposite upon the spectrum?
2. Which color is at the other end of the spectrum of red?
3. 
Q2:
1. What color is red next to on the spectrum?
2. Which color is red right by on the spectrum?
3. 
Q3:
1. What is the red light's wavelength range?
2. How long is a red light wave?
3. 
Q4:
1. What is meant by the acronym RGB?
2. What is RGB short for?
3. 
Q5:
1. What is RYB short for?
2. What does RYB stand for?
3. 
Q6:
1. How does blood become red?
2. What gives blood its red hue?
3. 
Q7:
1. How do geological areas become red?
2. What gives geological areas their red hue?
3. 
Q8:
1. How does the sky become red at sunset?
2. What imparts a red hue upon the sky at the end of the day?
3. 
Q9:
1. Does Rayleigh scattering apply to the sunrise?
2. Is red at sunrise and sunset caused by the same phenomenon?
3. 
Q10:
1. What makes autumn leaves red?
2. What pigment imparts a red hue onto fall leaves?
3. 
Q11:
1. When the sun is low or below the horizon, does the red wavelength decrease the light that reaches the eye?
2. Does less light reach our eyes when the sun is low or below the horizon and is this caused by red wavelength?
3. 
Q12:
1. What percentage of humans have red hair?
2. What percent of people are redheads?
3. 
