2.3 Light TED talk

Properties of Light

  • Light has color, which is a critical property to understand.

  • To comprehend color, it's beneficial to think of light as a wave.

Understanding Waves

  • Waves exhibit repetitive or periodic motion, exemplified by a cork bobbing in the ocean.

  • The cork's motion follows a consistent path: up and down repeatedly.

  • The time for the cork to complete one full cycle is the wave's period (e.g., 2 seconds).

  • Frequency is the measure of how often waves pass in one second.

    • In this example:

      • Period = 2 seconds → Frequency = 0.5 waves/second.

Light as a Wave

  • Light also has frequency, which relates directly to its color.

  • Color is essentially a measure of the frequency of light waves.

  • Our eyes detect these frequencies, but cannot see light’s periodic motion due to its rapid frequency (e.g., over 400 million times/second).

  • Visible spectrum:

    • Lowest frequency: Red

    • Highest frequency: Purple

    • Intermediate frequencies create a continuous band of color.

Interaction of Color with Objects

  • An object's color is determined by the light it reflects:

    • A yellow pencil reflects yellow light and absorbs other colors (blue, purple, red).

    • Blue objects reflect blue light, red objects reflect red, etc.

  • White objects reflect all colors; black objects absorb all frequencies.

  • Absorption of certain light frequencies by objects can generate heat (why dark clothes feel hot in sunlight).

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