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Learning what happens when light is soaked up by an object instead of bouncing off or passing through.
Have you ever wondered why walking barefoot on dark pavement in the summer feels like walking on a hot stove, but the white lines painted on the road feel much cooler?
Light is a form of energy. When light hits an object, it doesn't always bounce off. Sometimes, the object "soaks up" the light like a sponge soaking up water. This process is called absorption. When an object absorbs light, that light energy doesn't just disappear. Instead, it changes into thermal energy, which is what we call heat. The more light an object absorbs, the more thermal energy it creates, making the object feel warm to the touch.
Quick Check
When light is absorbed by an object, what does the light energy turn into?
Answer
It turns into thermal energy (or heat).
Why are some things hotter than others? It often comes down to color. Different colors treat light differently. Dark colors, especially black, are excellent at absorbing light. They take in almost all the light energy that hits them. Light colors, like white, are the opposite. They reflect most of the light away. Because dark colors absorb more light energy, they transform more of it into heat, which is why a black car feels hotter than a white car on a sunny day.
Imagine you have two t-shirts: one is jet black and one is bright white. 1. You lay both shirts outside in the direct sunlight for 20 minutes. 2. The black shirt absorbs nearly of the light hitting it. 3. The white shirt reflects most of the light. 4. When you touch them, the black shirt feels much hotter because it converted more light into heat.
Quick Check
Why does a white shirt stay cooler than a black shirt in the sun?
Answer
Because the white shirt reflects most of the light, while the black shirt absorbs it and turns it into heat.
We use the science of absorption every day! Engineers design solar panels to be dark (usually black or dark blue) so they can absorb as much sunlight as possible to create electricity. On the other hand, people living in very hot, sunny places often paint their houses white. This helps the buildings stay cool by reflecting the sun's energy away instead of absorbing it and heating up the inside of the home.
Even though a polar bear looks white, its skin underneath the fur is actually black! 1. The white fur helps the bear hide in the snow (reflection). 2. However, any sunlight that reaches the skin is absorbed by the black color. 3. This helps the bear stay warm in the freezing Arctic by turning that light into .
What happens to the temperature of an object as it absorbs more light?
Which of these surfaces would likely be the COOLEST to touch after sitting in the sun?
True or False: Light energy is destroyed when it is absorbed by an object.
Review Tomorrow
Tomorrow, try to explain to a friend why people wear light colors in the summer instead of dark colors using the word 'absorption'.
Practice Activity
Find two objects outside—one dark and one light. Touch them both and see if you can feel the difference in how much light they absorbed!