Waves and Electromagnetic Spectrum Flashcards

Vocabulary flashcards covering sound wave experiments, general wave properties, Doppler effect, longitudinal and transverse waves, and the electromagnetic spectrum with practical uses and hazards.

Echo Speed Formula

$v = \frac{2d}{t}$, used to measure the speed of sound when sound reflects off a surface back to the source.

Expected Speed of Sound in Air

$$343\,m/s$$

Accuracy Improvement for Speed of Sound Experiment

Measure over a longer distance to increase wave travel time, making time easier to measure accurately relative to human reaction time (e.g., measuring $5\,seconds$ is easier than $0.5$).

Human Hearing Range

$20\,Hz$ to $20,000\,Hz$ ($20\,kHz = 20,000\,Hz$).

Pitch and Frequency Relationship

High pitch corresponds to high frequency, and low pitch corresponds to low frequency.

Amplitude and Loudness Relationship

Large amplitude results in a louder sound, whereas small amplitude results in a quieter sound.

Refraction

The change in direction of a wave when it enters a different medium due to speed changes. Speed and wavelength change (decreasing in a denser medium), while frequency remains the same.

Doppler Effect

The observed change in frequency and pitch of a wave when a source moves relative to an observer, caused by compressing or spreading out of wavefronts.

Doppler Effect (Approaching Source)

When a wave source comes closer, wavefronts compress, causing wavelength to decrease and observed frequency and pitch to increase.

Doppler Effect (Receding Source)

When a wave source moves away, wavefronts spread out, causing wavelength to increase and observed frequency and pitch to decrease.

Amplitude

The maximum displacement of a point on a wave from its rest position.

Wavelength ($\lambda$)

The distance between two corresponding points on consecutive waves (e.g., trough to trough).

Frequency ($f$)

The number of complete waves passing a point each second, measured in Hertz ($Hz$).

Time Period ($T$)

The time taken for one complete wave to pass a point.

Frequency and Time Period Equation

$$f = \frac{1}{T}$$

Wave Speed Formula

$v = f \times \lambda$ (wave speed = frequency $\times$ wavelength).

Transverse Waves

Waves where the vibrations are perpendicular to the direction of wave travel (e.g., light, water waves); they feature crests and troughs and do not require a medium.

Longitudinal Waves

Waves where the vibrations are parallel to the direction of wave travel (e.g., sound); they feature compressions and rarefactions and require a medium.

Compressions

Regions in longitudinal waves where particles are pushed close together.

Rarefractions

Regions in longitudinal waves where particles are spread out.

Visible Light Hazard

Blindness in severe exposure.

Ultraviolet Hazards

Skin tissues can be ionized, causing skin cancer and sunburn.

X-rays Hazards

Mutates DNA and kills cells, or causes cancer.

Gamma Rays Hazards

Ionizes atoms in living tissue.

Electromagnetic Spectrum Mnemonic

"Red Meat Is Very Unhealthy X-cept Gamma" (Red Radio Waves, Meat Micro Waves, Is Infra-red, Very Visible Light, Unhealthy Ultra-violet, X-cept X-rays, Gamma Gamma rays).

Radio Waves Properties and Uses

Lowest frequency ($10^4\,Hz$) and longest wavelength ($10^3\,m$); used for radio and television communications and broadcasting. Presents no threat.

Microwaves Uses

Satellite communications and cooking food.

Infra-red Uses

Electrical heaters and remote controls.

Visible Light Properties and Uses

Wavelength of $0.5 \times 10^{-6}\,m$ and frequency of $10^{15}\,Hz$; used for photography and vision.

Ultraviolet Uses

Sterilization and fluorescent lamps.

X-rays Uses

Medical vision/imaging and airport security scanners.

Gamma Rays Properties and Uses

Highest frequency ($10^{20}\,Hz$) and shortest wavelength ($10^{-12}\,m$); used for sterilizing medical equipment and killing cancer cells.

General Properties of EM Waves

EM waves are transverse, transfer energy without matter, require no medium, and travel at the same speed in all mediums.