Study Notes on Electromagnetic Spectrum and Properties of Light

Electromagnetic Spectrum

  • Different types of Electromagnetic Radiation have different wavelengths.

  • The Electromagnetic Spectrum can penetrate the Earth’s atmosphere.

Wavelengths (in meters) and Frequencies (in Hz)

  • Radio:

    • Wavelength: 10310^3

    • Frequency: 10410^4

    • Temperature of bodies emitting: 1K

  • Microwave:

    • Wavelength: 10−210^{-2}

    • Frequency: 10810^8

    • Temperature of bodies emitting: 100K

  • Infrared:

    • Wavelength: 5imes10−65 imes 10^{-6}

    • Frequency: 101210^{12}

    • Temperature of bodies emitting: 10,000K

  • Visible:

    • Wavelength: 10−810^{-8}

    • Temperature of bodies emitting: 10 Million K

  • Ultraviolet:

    • Wavelength: 10−1010^{-10}

  • X-ray:

    • Wavelength: 10−1210^{-12}

  • Gamma Ray:

    • Wavelength: 10−1210^{-12}

Energy and Frequency

  • As we decrease in wavelength, we increase energy and frequency.

  • Example:

    • X-rays have HIGH energy and a SHORT wavelength.

    • Radio waves have LOW energy and a LONG wavelength.

Properties of Light

  • White light is a mixture of the seven colors of the rainbow.

  • Different colors of light have different wavelengths.

  • Demonstration:

    • White light can be split using a prism, demonstrating how rainbows are formed through raindrop refraction.

Light Speed in Medium

  • Light travels at a slower speed through a prism than through a vacuum.

  • Energy dependency:

    • Red light (least energetic) is slowed down the least.

    • Violet light (most energetic) is slowed down the most.

Color Theory

Colors of the Rainbow

  • The sequence of colors is remembered by the acronym: Roy G. Biv.

    • Red

    • Orange

    • Yellow

    • Green

    • Blue

    • Indigo

    • Violet

Color Mixing

  • White light can be separated to produce different colors.

  • Color combinations:

    • Adding blue and red creates magenta (purple).

    • Adding blue and green creates cyan (light blue).

    • Adding all three RGB colors results in white.

    • Adding red and green yields yellow.

Types of Color Mixing

  • Addition (Light):

    • Primary colors: Red, Green, and Blue.

  • Subtraction (Pigments/Paint):

    • Primary colors: Cyan, Magenta, and Yellow.

Seeing Things

  • Luminous Objects:

    • Defined as objects that produce light.

    • We perceive light emitted directly from these objects.

  • Non-Luminous Objects:

    • Defined as objects that reflect light rather than produce it.

    • Visibility depends on light reflecting off them, which then hits our eyes.

Seeing Color

  • The appearance of an object's color depends on the colors of light it reflects.

    • Example:

    • A red book reflects only red light when illuminated by white light.

    • This means only red light is reflected, making the object appear red.