Light Waves Module 2 Notes

Properties and Behaviors of Light

Light as Electromagnetic Radiation

• Light is a type of electromagnetic radiation, consisting of photons (particles of light).

• Travels at a speed of 300,000 km/s (3 x 10^5 m/s), denoted by the symbol c.

Wave Properties

• Wave Behavior: Light transmits energy and information without physical transport of material.

• Crest: The highest point of a wave.

• Trough: The lowest point of a wave.

• Amplitude: Maximum displacement from its undisturbed state; greater amplitude indicates a larger disturbance.

• Wavelength: Distance between successive crests or troughs; shorter wavelengths correlate with higher energy.

• Wave Period: Time taken for one cycle of a wave to pass.

• Frequency: Number of waves passing a point in one second (measured in Hertz). Higher frequency equals more energy.

• Wave Speed Equation: Wave speed = frequency x wavelength.

Properties of Electromagnetic Waves

• Medium Requirement: Most waves require a medium to travel through, but electromagnetic waves are unique—they require no medium and can travel in a vacuum.

• Types of Electromagnetic Waves: Gamma rays, X-rays, ultraviolet, visible light, infrared, radio waves, microwaves.

• Visible Light Spectrum: Human perception of visible light is limited compared to other electromagnetic radiation.

• Telescopes: Used to measure electromagnetic radiation include radio, optical, and infrared telescopes.

Laws Related to Electromagnetic Radiation

Wien’s Law

• Peak wavelength (λ_peak) is inversely proportional to temperature (T).

Stefan-Boltzmann Law

• Total flux (F) is proportional to T^4 (the fourth power of temperature).

• Higher flux allows more electromagnetic radiation to pass through a given area.

Applications of Electromagnetic Radiation

• Treatments and Effects:

  • Ultraviolet light can cause sunburn.

  • X-rays are used to view broken bones.

  • Gamma rays are utilized in cancer treatment.

• Blocking of EM Radiation: Atmosphere blocks most forms of radiation, measured in terms of opacity (higher opacity blocks more radiation).

• Everyday objects emit blackbody radiation in the infrared spectrum, relevant in medical diagnostics such as:

  • Breast cancer detection.

  • Heart disease diagnosis.

  • Pre-stroke prediction.

Characteristics of Blackbody Radiation

• Intensity of radiation varies by wavelength.

• Peak intensity occurs at a specific wavelength, decreasing on either side.

Wave Behaviors

• Diffraction: Bending of waves around obstacles.

• Interference: The sum of two waves can yield larger (constructive) or smaller (destructive) amplitudes.

Atoms and Motion

• All matter comprises atoms, which are perpetually in motion; higher temperatures correlate with increased motion.

• Atoms collide and release energy in the form of light.

Temperature Scales

Kelvin Temperature Scale

• 0 degrees K: All thermal motion ceases.

• 273 degrees K: Water freezes.

• 373 degrees K: Water boils.

Concluding Thoughts on Light

• As a wave, light exhibits diffraction and interference.

• As a particle, it consists of photons that carry energy.