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).