Physics 19 Questions

a periodic wiggle in time is called a *vibration*, while a wiggle in space and time is a *wave*. Think of a single guitar string vibrating, while a large swell of ocean water is a wave!

The source of all waves, whether mechanical or electromagnetic, is something that is vibrating.

the time a pendulum takes to swing to-and-fro. This is only dependent on the length of the pendulum, not the mass or size or arc.

The long pendulum has the longer period. The period is proportional to the length.

A sine curve is a pictorial representation of a wave, produced by simple harmonic motion.

Period is the time from one crest to the next, amplitude is the distance from the midpoint to a crest, wavelength is the distance from one crest to the next, and frequency is the number of crests that pass per second.

time from one crest to the next.

distance from the midpoint to a crest. Think visual amplitude on sound board from flat bottom screen to its possible height.

distance from one crest to the next crest, or between any two identical points of the wave.

number of crests that pass per second.

101,700,000 vibrations 1 vibration per second = 1Hz, 1 million vibrations per second = 1MHz

Frequency and period are inversely proportional. Frequency = 1/period Period = 1/Frequency

disturbance. Energy can be transferred from source to receiver without transfer of matter. What is propagated is the disturbance, not the medium through which is transferred. The medium returns to its initial condition after the disturbance has passed.

No. The medium returns to its initial condition after the disturbance has passed.

At right angles to the direction of wave travel.

Parallel to the direction of wave travel. "Motion is along the direction of the wave rather than at right angles to it."

The wavelength is the distance between successive maximum compressions (or rarefractions).

Wave speed is frequency multiplied by wavelength. w speed = frequency X wavelength

When two or more waves occupy the same space, wave displacements add at every point.

Constructive interference occurs when the crests of two waves add together. Destructive interference occurs when a crest of one wave is reduced by the trough of another.

All waves show interference, whether water, light, or sound. The overlapping of waves forms an interference pattern. Crest over Crest = constructive interference with increased amplitude. Crest over Trough = destructive interference with reduced amplitude.

In a standing wave, a node always has zero displacement and an antinode always has maximum displacement. The incident and reflected waves will form a standing wave, where *nodes* appear to be standing still, and *antinodes* are regions of maximum displacement and maximum energy.

standing waves can be produced with either transverse or longitudinal vibrations.

Only frequency changes. Both the frequency and wavelength undergo change when the source is moving, but the wave speed does not.

Both. This includes light and sound.

An approaching source has increased light frequency towards the high-frequency end of the color spectrum - a blue shift. A receding source has a decreasing frequency towards the low-frequency spectrum end - a red shift.

As fast as the wave speed; as fast as or faster than the wave speed. When the bug swims as fast as the speed of the waves it produces, the waves pile in front of the source. When it outruns the waves it produces, it will always be entering water with a smooth surface.

As fast as or faster than the speed of sound.

The angle of the V gets smaller as the speed of the source gets faster.

A shock wave in air is three-dimensional.

False. An aircraft creates a shock wave continuously as it is supersonic. This is heard as a sonic boom by an observer. The "barrier" is not real; an aircraft with sufficient power easily travels faster than the speed of sound. It reaches the ground to listeners below, who hear the sharp crack.

False. A whip and a bullet move through the air without making sounds other than the shock wave. Once an object is moving faster than the speed of sound, it will *make* sound. Neither are sound sources, but when traveling at supersonic speeds, will produce their own sounds as they generate shock waves.

This is characteristic of the Doppler effect, meaning the Sun's motion leads to a change in frequency on its edges.

increase. A shorter pendulum swings to and fro more frequently than a longer one.

decrease. A short pendulum has a shorter period time of to and fro swing than a long pendulum.

To provide a transverse wave to a Slinky, impart a continuous up and down motion. The motion of the Slinky is transverse to the direction the wave travels. For a longitudinal wave, push and pull the end of the Slinky. Motion will be along the direction of the wave.

Approaching the source and close the the source, the listener will hear higher frequencies. As the listener pulls away and further from the source, the frequency will decrease with distance, as the waves will take longer to reach the listener.

In the same continuous vicinity as your car, a same speed traveling car would not hear an increased frequency, but a constant frequency. If you were to pull away from the second car, the listener would hear decreased frequency with distance.

This could be considered a "water boom", as the fish speeds through the water, entering water with an undisturbed area.