Wave Properties and Light Reflection

Wave Properties

• Waves transfer energy without transferring matter.
• Wave motion is demonstrated by vibrations in ropes, springs, and water waves.
• Wave features include wavefront, wavelength, frequency, crest, trough, amplitude, and wave speed.
• Wave speed (v) = frequency (f) × wavelength (λ).
• Transverse waves vibrate perpendicular to propagation (e.g., electromagnetic radiation, water waves, seismic S-waves).
• Longitudinal waves vibrate parallel to propagation (e.g., sound waves, seismic P-waves).
• Waves can be reflected, refracted, and diffracted.
• Reflection, refraction, and diffraction are demonstrated using ripple tanks.
• Diffraction depends on wavelength and gap size.

Light Reflection

• Key terms: normal, angle of incidence, angle of reflection.
• Plane mirrors create images that are the same size, same distance from the mirror, and virtual.
• Angle of incidence = angle of reflection.
• Reflection can be analyzed using constructions, measurements, and calculations.

Light Refraction

• Key terms: normal, angle of incidence, angle of refraction.
• Refraction can be observed by analyzing light passing through transparent blocks of different shapes.
• Refraction involves light passing through a transparent material between two boundaries.
• Critical angle is the specific angle for internal reflection.
• Internal reflection occurs when light travels from a denser to a less dense medium.
• Total internal reflection occurs when the angle of incidence exceeds the critical angle.
• Refractive index (n) = speed of light in medium 1 / speed of light in medium 2.
• n = sin i / sin r
• n = 1 / sin c
• Optical fibers utilize total internal reflection for telecommunications.

Thin Lenses

• Converging and diverging lenses affect parallel light beams differently.
• Key terms: focal length, principal axis, principal focus (focal point).
• Ray diagrams show real image formation by converging lenses.
• Image characteristics include size (enlarged/same/diminished), orientation (upright/inverted), and type (real/virtual).
• Virtual images are formed by diverging rays that appear behind the lens.
• Ray diagrams show virtual image formation by converging lenses.
• Single lenses can act as magnifying glasses.
• Lenses correct long-sightedness and short-sightedness.

Light Dispersion

• Light dispersion is demonstrated by the refraction of white light through a prism.
• The visible spectrum has seven colors (traditional order) in frequency and wavelength order.
• Monochromatic light has a single frequency.

Electromagnetic Spectrum

• The electromagnetic spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
• All electromagnetic waves travel at the same speed in a vacuum (approximately 3.0 × 10⁸ m/s).
• Various uses tailored for each portion of the spectrum are listed (e.g., radio waves for radio transmission, microwaves for satellite TV, visible light for vision).
• Excessive exposure to certain electromagnetic radiation types can be harmful; specific examples are detailed.
• Microwaves cause internal heating, infrared causes burns, ultraviolet damage cells/eyes, X-rays/gamma rays cause mutations/cell damage.
• Communication with satellites primarily uses microwaves.
• Digital signals offer advantages like faster data transmission and longer range.

Sound

• Sound is produced by vibrating sources.
• Sound is a longitudinal wave.
• Humans can hear frequencies from 20 Hz to 20,000 Hz.
• Sound needs a medium to travel.
• Sound speed in air is approximately 330–350 m/s.
• Sound waves consist of compressions and rarefactions.
• Sound speed is fastest in solids, then liquids, then gases.
• Measuring distance and time can determine sound speed.
• Amplitude and frequency changes affect loudness and pitch.
• Echoes are sound wave reflections.
• Ultrasound is sound above 20 kHz.
• Ultrasound applications include nondestructive testing, medical scanning, and sonar.