Waves, sound and light Flashcards
Define pulse
A single disturbance that moves along or through a medium, while the overall medium does not change.
Medium
Material through which a wave travels
Amplitude
Maximum distance that particles move from their rest position.
Transverse wave
Wave where movement of particles of the medium is perpendicular to the direction of propagation of the wave.
Wavelength
Distance between any two adjacent points in phase
Period
Time taken for 2 successive crests or troughs to pass a fixed point
Frequency
Number of successive crests or troughs passing a given point in 1 second
Longitudinal wave
Wave where the particles in the medium move parallel to the direction of propagation of the wave
Compression
Region in a longitudinal wave where the particles are closest together
Rarefaction
Region in a longitudinal wave where particles are furthest apart
Sound Waves
- Pressure waves
- Travels fastest in solids, slightly slower in liquids and
slowest in gases - Compressions and rarefactions are created as the sound source vibrates
- source vibrates longitudinally and the longitudinal motion of air produces pressure fluctuations
Speed of sound
- Dependent on medium
- Faster in denser substances
- Depends of temperature
- Influenced by pressure of medium
Reflection and echoes
- When sound waves collide with an object they are reflected
- sound is reflected in large open spaces where there is a very large object present causes an echoe
Pitch
- Depends on frequency
- High frequency = higher pitch
- Low frequency = Low pitch
Loudness
- Depends on Amplitude
- Larger amplitude = louder sound
- Smaller amplitude = softer sound
- Also dependent on ear sensitivity
Ultrasound
- Frequency between 20-150 kHz
- High frequency and short wavelengths
Uses of Ultrasound
- Bats send out ultrasound signals which are reflected to detect positions of objects
- Dolphins send out ultrasound signals to detect objects further away
- Detects weak spots in metal objects
- Thickness of metals and plastics
- Clean delicate mechanisms of old fashioned watches
Noise
Sound consisting of a large number of unrelated different frequencies
Electromagnetic Radiation
No medium required wave
How does EM radiation work?
- Result of accelerating charges
- Magnetic field produced around moving electric charge
- Oscillating magnetic field in turn producesa magnetic field in a plane at rights angles to it, which again produces an oscillating magnetic field
- Thus, EM radiation produced by magnetic and electric fields repeatedly creating each other
Order of EM radiation
Radio waves, Microwaves, infrared, visible spectrum, ultraviolet, X rays, Gamma rays
Photon
Energy packet of light
