Characteristics of Light Waves
Introduction to Light Waves
- Focus: Understanding frequency, wavelength, and their relationship to the speed of light.
- Goal: Comprehend why the speed of light ( c) is equal to wavelength ( ) times frequency ( ).
- Highlight the beauty of mathematics in describing nature.
Chapter 1: What Is Frequency?
- Frequency (ν): Symbolized by the Greek letter nu.
- Definition: The number of wave cycles passing a point per second.
- A wave cycle: One complete up/down motion.
Chapter 2: Relationship between Frequency and Wavelength
- Wavelength (λ): Represented by the Greek letter lambda.
- Definition: Distance between two consecutive wave cycles.
- Inverse relationship: Longer wavelength = lower frequency
- Shorter wavelength = higher frequency.
- Measurement of frequency: Expressed in cycles per second (s⁻¹) or Hertz (Hz).
Chapter 3: The Speed of Light
- Speed of light (c): 3 x 10⁸ m/s or 300 million m/s.
- Example: Signal from Earth to a friend 300 million meters away takes 1 second.
- More realistic example: Light from the Moon takes 1.23 seconds to reach Earth, reflecting past events on the Moon.
Chapter 4: Speed of Light
- Scientific notation: Speed of light is often expressed as 3 x 10⁸ m/s.
- This remarkable speed is consistent across different types of light waves, from visible light to radio waves, which all travel at the same speed.
Chapter 5: Visible Spectrum
- Visible light range: 400 - 700 nanometers.
- Types of light waves: Radio waves, microwaves, infrared, ultraviolet, X-rays, gamma rays.
- Importance: All move at the speed of light (3 x 10⁸ m/s).
- Relationship formula:
- Speed of light (c) = Wavelength (λ) x Frequency (ν)
- Calculation examples:
- Wavelength of 1 meter → frequency of 3 x 10⁸ Hz.
- Wavelength of 2 meters → frequency of 1.5 x 10⁸ Hz.
- Wavelength of 0.5 meters → frequency of 6 x 10⁸ Hz.
Chapter 7: Why Is the Speed of Light Always Equal to Wavelength Times Frequency?
- Inverse relationship between wavelength and frequency:
- As wavelength decreases, frequency increases proportionally.
- This relationship holds true due to the constancy of the speed of light.
- Conclusion: The equation λν = c describes a fundamental characteristic of light.
- Mathematics provides insight into natural phenomena, exemplified by the relationship described between frequency, wavelength, and the speed of light.
- An interesting thought: Light from the sun takes about 8 minutes and 19 seconds to reach Earth, emphasizing the vastness of space and the speed at which light travels.
