47. How Radiation Affects Temperature

All objects are constantly absorbing and emitting electromagnetic radiation. This balance determines the object's temperature.

Absorption vs. Emission: * Absorbing > Emitting: The object gains energy and gets warmer.
- Emitting > Absorbing: The object loses energy and gets cooler.
- Emitting = Absorbing: The object stays at a constant temperature.
Examples:
- A hot cup of tea emits more radiation than it absorbs from its surroundings, so it cools down.
- An ice cube absorbs more radiation than it emits, so it warms up.

Intensity: This is the power of the radiation per unit area. It measures how much energy radiation transfers to an area in a certain time.
The Radiation Graph:
- The x-axis shows wavelength (UV, visible light, infrared).
- The y-axis shows intensity.
Effect of Temperature:
- As temperature increases, the intensity of every wavelength increases (the curve gets higher).
- The peak intensity shifts toward shorter wavelengths (the curve shifts to the left).
Visible Examples:
- Room temperature objects: Emit mostly infrared radiation, which we cannot see.
- Hot objects (like coal or the sun): Emit enough visible light for us to see them glow.
- Bunsen Burners: As they get hotter, the flame color shifts from orangey-red (longer wavelength) to blue (shorter wavelength).

The Earth's temperature is also a result of this radiation balance:

Incoming: The Earth is bombarded by electromagnetic radiation from the Sun.
Outgoing: As a warm object, the Earth emits its own infrared radiation back into space.
Atmosphere: The Earth's atmosphere complicates the balance by reflecting, absorbing, and emitting radiation.
Day vs. Night: * Day: More energy is absorbed than emitted, increasing the local temperature.
- Night: Less energy is absorbed than emitted, decreasing the local temperature.
Global Scale: Overall, the Earth's average temperature stays relatively constant because parts of the planet are always in sunlight while others are in darkness.