Waves Flashcards
What do waves transfer?
Energy, not matter.
What are the two types of waves? What is the difference?
Transverse waves, where the direction of the vibration is perpendicular to the direction of the wave.
Longitudinal waves, where the direction of the vibration is parallel to the direction of the wave. They have compressions and rarefractions.
What are mechanical waves and electromagnetic waves?
Mechanical waves travel through a medium (substance) eg springs, sound.
Electromagnetic waves can travel through a vacuum eg light, radio.
What are all electromagnetic waves? What can mechanical waves be?
Electromagnetic waves are always transverse. Mechanical waves can be both.
What are the upmost and bottom most points of a wave?
Peaks and troughs.
What happens to the energy carried when amplitude is increased?
The energy carried increases.
What is the wavelength of a longitudinal wave?
The distance from the middle of one compression to the middle of the next compression.
What happens when a barrier is placed in front of a wave?
It is reflected.
How is a wave refracted?
The wave changes speed and wavelength when moving through a boundary between different substances. A change in direction of the wave is caused.
What can happen to a wave when it meets a boundary with a different substance?
- Totally or partially refracted.
- Transmitted through the substance.
- Absorbed by the substance.
What can sound waves not travel through?
A vacuum. They require a medium to transfer vibrations.
How is an echo produced?
Sound waves are reflected from a hard, flat surface.
What are the investigations for waves?
- Frequency generator and oscillator. Adjust the frequency of the oscillator until there is a single loop in the string. Note the frequency. Measure the length of the loop. Calculate the wavelength. Calculate the speed. Change frequency of oscillator to obtain more loops. Record wavelength and speed.
- Measure time taken for a wave to travel from one side or ripple tank to the other. Measure distance. Calculate speed. Change frequency and calculate wave speed each time.
What does pitch depend on? What does volume depend on?
Pitch depends on frequency. Volume depends on amplitude.
What is the range is frequencies for the human ear?
20 Hz to 20 kHz
What are ultrasound waves?
Waves with a high frequency than 20 kHz (20000 Hz)
How does an ultrasound scanner work?
When a wave meets a boundary between two different materials, part of the wave is refracted. The waves travel back to the transducer. The time taken to return is used to calculate distance to the boundary. The distance to the boundary is half the distance travelled by the wave. An image is processed.
Why are ultrasound waves used for medical scanning?
- It is reflected at boundaries between different types of tissue.
- It is non-ionising, so is safer than X-rays.
What waves do earthquakes produce?
Seismic waves.
What is the order of waves in an earthquake?
- P-waves - longitudinal, causing initial tremors. They refract at the boundary between mantle and core.
- S-waves - transverse waves, more slow, tremors after first minute. Can’t travel through liquid core.
- Both P and S waves bend through the mantle, as their speed gradually changes.
- L-waves - slowest, only travel through crust. Arrive last and cause violent movement.
How are earthquakes analysed?
Detectors on the surface called seismometers are found at different points around the world. The epicentre can be determined. The structure of the earth can be understood. Liquid inner core, solid outer, mantle, crust is 50km deep.
What is the electromagnetic spectrum order?
Radio Microwaves Infrared Visible light UV X-ray Gamma
How does frequency and wavelength change going down the spectrum?
From longest wavelength and smallest frequency to shortest wavelength and highest frequency.
What is the relationship between frequency and energy transferred?
The higher the frequency of the wave, the more energy it transfers.
