Sound and Waves Overview

Sound and Waves

• Sound is a wave that travels through a medium.
• Light is part of the electromagnetic spectrum.
• Understanding light requires knowledge of electromagnetic fields and wave motion.
• A wave is an oscillation of a physical quantity that moves through a medium (matter or space) and transfers energy.
• Examples of waves include Mexican waves, water waves, earthquakes, and electromagnetic waves (e.g., light, radio, and TV signals).
• Waves transfer energy but not matter. They move matter as they pass through it.
• Waves are categorized as transverse or longitudinal.
• Longitudinal waves move in the same direction as the wave (e.g., sound).
• Transverse waves oscillate perpendicular to the direction of wave motion (e.g., light).
• Some waves do not require a medium to travel, are called electromagnetic waves.
• Some waves require a medium, are called mechanical waves.

Wave Properties

• A simple wave is characterized by constant speed, perfect repetition, and constant height (amplitude).
• The constant distance between repeating points on a wave is the wavelength (λ).
• The number of waves passing a point in one second is the frequency (measured in Hertz).
• The energy of a wave is proportional to its amplitude.
• Amplitude is the height of a wave (crest to trough).
• Wavelength is the distance between two consecutive peaks (or troughs).
• Frequency is the number of waves that pass a point per second.

Describing Simple Waves

• Crest is the highest point of a wave.
• Trough is the lowest point of a wave.

Medium Oscillation and Wave

• In longitudinal waves, particles oscillate in the same direction as the wave (e.g., sound waves).
• In transverse waves, particles oscillate perpendicular to the direction of the wave (e.g., light waves).

Parts of Longitudinal Waves

• Compression: particles are close together.
• Rarefaction: particles are spread apart.

Transverse Waves

• In transverse waves, the medium moves perpendicular to the direction of wave motion.
• Crest: the highest point of a wave.
• Trough: the lowest point of a wave.

Wave Speed, Wavelength & Frequency

• Wave speed = wavelength × frequency (v = λf)
• Wave speed varies depending on the medium.
• Water waves travel at speeds from 1 to 20 m/s.
• Sound waves travel at 340 m/s.
• Seismic waves travel at 1000-14,000 m/s.
• Electromagnetic waves travel at 300,000,000 m/s.

Examples of Calculations

• Students can use known speeds of waves to calculate wavelength or frequency (and vice versa.)

Sound Waves, Hearing and the Human Ear

• The human ear has three parts: the outer, middle and inner ear.
• The outer ear collects sound waves.
• The middle ear transmits vibrations from eardrum to inner ear.
• The inner ear translates vibrations into nerve impulses.

Middle Ear

• Parts of the middle ear include the malleus, incus, and stapes.
• The parts work together to receive, amplify and transmit sound.

Internal Ear

• Parts of the internal ear include the cochlea, and semicircular canals.

Elements of Human Hearing

• The outer ear collects sound waves from the environment that hit the eardrum.
• The eardrum vibrates, causing the tiny bones of the middle ear (malleus, incus, and stapes) to vibrate.
• The vibrations are transferred to the inner ear (cochlea).
• The vibrations in the inner ear stimulate sensory hair cells that convert the mechanical energy into electrical signals.
• The electrical signals are sent to the brain via the auditory nerves where it is interpreted as sounds.

Sound Wave Speed vs Altitude

• Sound wave speed decreases with increasing altitude due to decreasing temperature.

Loudspeakers

• A loudspeaker converts electrical signals into sound.
• The electromagnet moves in response to changes in the electrical signal , causing the cone to vibrate, creating sound waves

Microphones

• A microphone converts sound into electrical signals.
• The speaker and microphone work in reverse from each other.

Interference

• Waves can pass through each other.
• In phase interference causes an increase in amplitude.
• Out of phase interference causes a decrease in amplitude.

Interference of two waves

• Waves can interfere constructively (adding up) or destructively (canceling out).
• Constructive interference occurs when waves are in phase.
• Destructive interference occurs when waves are out of phase.

Introduction to Electromagnetic Waves

• Electromagnetic waves are oscillating electric and magnetic fields.
• They propagate without a medium.
• They are produced by accelerating charges.

Electromagnetic Waves

• Electromagnetic waves have both electric and magnetic components.

Electromagnetic Spectrum

• The electromagnetic spectrum ranges from radio waves to gamma rays.
• Each type of wave has different frequencies and wavelengths.

Visible Light

• Visible light is a portion of the electromagnetic spectrum.
• Wavelengths of visible light range from wavelengths in the red end of the spectrum to the violet at the other end.

The Structure of the Eye

• The eye is an image-forming device.
• It contains parts like the lens, iris, and retina.

Image Formation in the Eye

• The lens in the eye focuses light to form an image.
• Images in the eye are inverted.
• The brain interprets the inverted image correctly.

Color and Vision

• The sensitivity of the eye to different colors depends on the three cone types (S, M, and L cones).

Examples of Calculations

• Students can use the speed of light to calculate the frequency given a wavelength, or to calculate the wavelength given a frequency.

Sources and Uses of Electromagnetic Waves

• Different types of electromagnetic waves have various applications (e.g., radio waves for communication, microwaves for cooking, visible light for vision, X-rays for medical imaging).

Light Scattering by the Atmosphere: Sky Colors

• Rayleigh scattering explains why the sky is blue.
• The scattering of light is dependent on wavelength of light.

Thermal Radiation

• Objects emit electromagnetic radiation due to their temperature.
• The hotter an object, the shorter the wavelength of its emitted radiation.

Solar Spectrum

• The sun's radiation spectrum includes visible, UV, and infrared light.

UV Radiation

• UV radiation is a type of electromagnetic radiation.
• It has shorter wavelengths as compared to visible light.
• It is given off by the sun.
• The ozone layer in the atmosphere protects the earth from harmful UV radiation.

The Atmosphere and UV Radiation

• The atmosphere absorbs different types of UV radiation at varying levels.
• The ozone layer is an important factor in absorbing UV radiation.

What is Ozone

• Ozone is a triatomic form of oxygen with the chemical formula O3.
• Ozone in the atmosphere is vital for absorbing harmful UV radiation,
• Ozone in Earth's lower atmosphere is detrimental to human health in the form of smog.

Ozone Depleting

• Ozone in the atmosphere is being depleted.
• Chemical catalysts (ex. chlorofluorocarbons) are breaking down ozone in the atmosphere.

Ozone Production

• Ozone molecules are created through various processes related to the interaction of oxygen molecules and UV radiation
• Ozone absorbs ultraviolet radiation and protects life from the harmful effects of radiation.

The Greenhouse Effect

• The greenhouse effect is a natural process that warms the Earth's surface.
• Gases in the atmosphere trap heat.
• Greenhouse gases (ex. CO2, H2O, methane) absorb and transmit infrared radiation from the Earth's surface.

Global Warming

• Human activities increase the concentration of greenhouse gases in the atmosphere, leading to a warming effect
• Global warming causes dangerous changes in the earth's climate.

Explore the fascinating world of sound and waves in this quiz. Learn about the differences between mechanical and electromagnetic waves, and understand the properties that define wave motion. This quiz will help reinforce your knowledge of how waves transfer energy and their various classifications.