Explain, in terms of absorbed and reflected light, why a blue object appears blue.

When we see the colors of the objects around us, we are witnessing light interaction at work. Light interaction is how light behaves when it encounters various materials. Imagine sunshine streaming down and striking an apple, a leaf, or a car. Depending on the object's surface properties, some light waves are absorbed, and others are bounced off or reflected.

The colors we observe are strictly the result of this reflection. If an object reflects most of the sunlight back, we would see it as white, and if it absorbs all the waves, the object would appear black to us. Now, think of a blue object as a selective mirror; it's not reflecting all light equally, but rather it is picky about which wavelengths it sends back to our eyes.

The absorption of light plays a pivotal role in dictating the color we perceive an object to be. Every object has a molecular composition that determines which wavelengths of light it will absorb and which it will reflect.

For something to appear blue, it must absorb most of the other colors of the light spectrum—reds, yellows, and greens, for instance—while reflecting the blue wavelengths vigorously. This specific preference in light absorption is due to the object’s chemical structure. Pigments and dyes, often seen in fabrics, paints, and natural features, have compounds that are structured to absorb certain wavelengths and not others, creating the colorful world we enjoy.

Our perception of color is not just an objective phenomenon—it's a subjective experience involving the eyes and brain. When light waves reflecting off objects enter the eye, they strike the retina, where rod and cone cells detect them. The cones are responsible for color vision, and different types of cones are sensitive to different wavelengths of light.

Humans typically have three types of cones, each one tuned to red, green, or blue wavelengths. The brain combines the signals from these cones to create the full spectrum of colors we can see. When a blue object reflects blue light, the blue-sensitive cones in our eyes are stimulated, sending a message to the brain that says, 'this is blue.' Thus, the object is perceived as blue not only because of its physical properties but also because of our eyes' and brain's interpretation of the reflected light.