General Physics 2 - Wave
Phenomena
• Learning Competencies for Grade 12
Introduction
• • Waves describe how energy propagates.
• • Important for communication, acoustics,
and real-world applications.
Inverse-Square Law & Wave
Intensity
• • Intensity decreases as square of distance.
• • Formula: I ∝ 1/r²
• • Example: Sound waves from a speaker.
Sample Problem - Inverse-Square
Law
• A speaker emits a sound wave with an
intensity of 40 W/m² at 2 meters. What is the
intensity at 6 meters?
• Solution:
• I₂ = I₁ (r₁² / r₂²)
• I₂ = 40 (2² / 6²) = 40 (4/36) = 4.44 W/m²
Superposition of Waves
• • Overlapping waves combine amplitudes.
• • Constructive & Destructive Interference.
• • Equation: y = y₁ + y₂.
Sample Problem - Superposition
• Two waves with amplitudes of 3 cm and 5 cm
interfere constructively. What is the resultant
amplitude?
• Solution:
• A = A₁ + A₂ = 3 cm + 5 cm = 8 cm
Standing Waves on a String
• • Reflection creates nodes (no motion) &
antinodes (max motion).
• • Formula: L = n(λ/2)
• • Example: Guitar strings.
Sample Problem - Standing Waves
• A string has a length of 1.5 m and vibrates in
its 3rd harmonic. What is the wavelength of
the standing wave?
• Solution:
• L = n(λ/2)
• 1.5 = 3(λ/2)
• λ=1m
Doppler Effect
• • Frequency change due to relative motion.
• • Formula: f' = f ( (v ± v₀) / (v ∓ vₛ) ).
• • Example: Ambulance siren effect.
Sample Problem - Doppler Effect
• A stationary observer hears an approaching
ambulance with a siren at 500 Hz. If the
ambulance moves at 30 m/s and the speed of
sound is 340 m/s, what frequency does the
observer hear?
• Solution:
• f' = f ( v / (v - vₛ) )
• f' = 500 (340 / (340 - 30)) = 547 Hz
Summary & Applications
• • Inverse-Square Law: Explains sound/light
weakening.
• • Superposition: Noise cancellation.
• • Standing Waves: Musical instruments.
• • Doppler Effect: Radar, astronomy.
Assessment Questions
• • How does wave intensity change with
distance?
• • What happens in constructive interference?
• • What conditions create standing waves?
• • How does motion affect frequency
perception?
References & Credits
• • Cite textbooks, websites, and curriculum
guides.
• • Acknowledge any external resources used.