Waves and Electromagnetic Spectrum Lecture Notes

Waves Overview

• Waves Transfer: Energy transfer without moving matter.
• Types of Waves:
  • Transverse Waves: Vibrations are perpendicular to the direction of energy transfer (e.g., water waves, electromagnetic waves).
  • Longitudinal Waves: Vibrations are parallel to the direction of energy transfer (e.g., sound waves).

Transverse Waves

• Characteristics:
  • Vibration direction: Up and down.
  • Propagation direction: Horizontal.
  • Examples: Water waves, Slinky waves.
• Wave Parts:
  • Crest: Highest point.
  • Trough: Lowest point.

Longitudinal Waves

• Characteristics:
  • Vibration direction: Forward and backward.
  • Propagation direction: Horizontal.
  • Examples: Sound waves, seismic primary waves.
• Wave Parts:
  • Compression: Particles are close.
  • Rarefaction: Particles are far apart.

Describing Waves

• Displacement-Time Graph: Shows wave cycles.
• Amplitude (A): Energy carried by the wave.
• Wavelength (λ): Distance between identical points.
• Frequency (f): Vibrations per second (Hz).
• Period (T): Time for one cycle (s).

Wave Speed

• Speed (v): Distance traveled per unit time.
  • Formula: v = λ × f

Wavefronts

• Wavefronts: Lines along peaks/compressions.
• Ripple Tank: Demonstrates wavefronts in water.

Reflection of Waves

• Reflection: Waves bounce off obstacles.
  • Angle of Incidence (i) = Angle of Reflection (r).

Refraction of Waves

• Refraction: Change in wave speed when moving between mediums.
  • Deep to Shallow Water: Speed decreases, wavelength decreases.

Doppler Effect

• Doppler Effect: Frequency change due to source movement.
  • Compressed Waves: Higher frequency, higher pitch.
  • Stretched Waves: Lower frequency, lower pitch.

Electromagnetic Spectrum

• Properties: All transverse, travel through vacuum, constant speed in vacuum.
• Order: Radio waves to gamma rays (longest to shortest wavelength).
• Uses:
  • Radio Waves: Communication.
  • Microwaves: Cooking, radar.
  • Infrared: Heating, thermal imaging.
  • Visible Light: Vision, data transmission.
  • Ultraviolet: Sterilization.
  • X-rays: Medical imaging.
  • Gamma Rays: Cancer treatment.

Harmful Effects of EM Waves

• Higher Frequency Waves: More ionizing, can cause cancer.
• Protection: Limit exposure, use protective gear.

Light Waves

• Reflection: Mirrors reflect light at equal angles.
• Refraction: Bending of light when passing through mediums.
• Refractive Index (n): Measure of bending.
  • Formula: n = sin(i) / sin(r)

Total Internal Reflection

• Occurs: When light travels from a denser to a less dense medium and the angle is greater than the critical angle.
• Applications: Periscopes, binoculars, optical fibers.

Sound Waves

• Characteristics: Longitudinal, require a medium.
• Speed: Varies by medium (faster in solids).
• Reflection and Refraction: Similar to light.
• Pitch and Frequency: Related to wavelength.

Practical Applications

• Sound Speed Experiment: Use echoes or timing methods.
• Use of Oscilloscope: Visual representation of sound waves.

(Note: Understanding these concepts is essential for mastery of the syllabus as noted by the lecturer.)

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