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.