Physics Exam Notes on Electromagnetic Radiation and Sound Waves

Relationship Between Frequency, Wavelength, and Amplitude

• In sound waves:

  • Frequency: Number of cycles per second (measured in Hertz, Hz) that affects the pitch of the sound.

  • Wavelength: The distance between successive peaks of a wave; inversely related to frequency.

  • Amplitude: Height of the wave, related to loudness; greater amplitude = louder sound.

Physical Qualities of Sound

• Frequency influences the pitch of sound:

  • Higher frequency = higher pitch.

  • Example: A 400 Hz tone has a higher pitch than a 200 Hz tone.

Sound Velocity

• The velocity of sound is affected by:

  • Medium: Sound travels faster in solids than liquids and faster in liquids than gases.

  • Temperature: Velocity increases with temperature in gases.

Electromagnetic Radiation (EMR) Basics

• The relationship between wavelength (BB) and frequency (f):

  • Formula: $v = f ext{λ}$ where:

  • $v$ = velocity (for light, $c$ in vacuum)

  • $f$ = frequency

  • $ext{λ}$ = wavelength

  • For light specifically, $c = f ext{λ}$ where:

  • $c = 3.00 imes 10^8 m/s$ (speed of light)

The Visible Light Spectrum

• Visible light constitutes approx. 0.0035% of the EMR spectrum.

• Ranges from red (lower frequency) to violet (higher frequency).

How We See Color

• The color perceived is the wavelength that is reflected:

  • White Light: Combination of all wavelengths (all colors reflected).

  • Black Objects: Absorb all wavelengths (no light reflected).

Color Addition vs Subtraction

• Color Addition:

  • Adding light to create new colors; primary colors of light are red, green, and blue.

  • Secondary colors: magenta, cyan, yellow.

  • Used in screens and lighting technologies.

• Color Subtraction:

  • Removing wavelengths to create color; used in inks and paints.

Diffraction

• Light spreading out when passing through a small slit due to wave interference:

  • Creates a pattern of alternating light and dark bands called fringes.

Polarization

• Filtering of light waves to allow only specific vibration directions:

  • Horizontal light amplification can create glare; polarized sunglasses help reduce glare.

Index of Refraction

• Defines how much light slows down in a medium:

  • Formula: $n = \frac{c}{v}$ where:

  • $n$ = index of refraction

  • $c$ = speed of light in a vacuum

  • $v$ = speed of light in the medium

• Light travels slowest in materials such as diamond.

Refraction

• Change in light direction and speed when transitioning between mediums:

  • Bends towards the normal in denser materials, away in less dense materials.

• Governed by Snell's Law: $n<em>1 ext{sin}(θ</em>1) = n<em>2 ext{sin}(θ</em>2)$.

EMR Characteristics

• Inverse relationship between frequency and wavelength:

  • Higher frequency = shorter wavelength, more photon energy.

  • Longer wavelengths are less affected by refraction and scattering (causing blue skies).

Light Wave and Particle Duality

• Light exhibits both wave and particle properties:

  • Wave behavior is demonstrated through polarization and diffraction.

  • Particle properties observed in the photoelectric effect with photons acting as particles.