TEMA: SISTEMA DE MEDIDA ANGULAR

GENERAL WAVE PROPERTIES

WHAT ARE WAVES?Waves are moving energy. Light energy moving from the computer screen to your eye moves as light waves. Sound energy moving from a radio to your ear moves as sound waves.

Waves can move along ropes, strings or across the surface of water. Some waves can even travel through space. When waves move along, they make the surface or object move in regular patterns often calledwave disturbances.

The important thing to notice is that no'matter'is moved with the wave. Water waves, which move the water particles up and down on the spot don't actually move any water along with the wave. Only the energy travels along.

Transverse and longitudinal waves

All waves can be put into two groups: Transverse waves Longitudinal waves

Fsica 11 de secundaria

1Profesor: Javier Trigoso T.

In transverse waves the particles vibrate at right angles to the movement of energy.

Examples are light waves, water waves and all electromagnetic waves.In longitudinal waves the particles vibrate in the same direction as the movement of energy.

Examples are sound waves and seismic waves.

WAVE WORDSTo compare waves we need to be able describe their characteristics, these include:

Amplitude Wavelength Time period Frequency

The amplitude of a wave is the height of the wave from the middle to a peak or trough. This is often called themaximum displacementof the wave. (The displacement of a particle is the distance a particle moves from thecentre)

Watch out. Many students make the mistake of measuring from a peak to a trough that gives double the correct answer.

The wavelength is the length of one complete wave. It can be measured, on a distance graph, from any point to the next similar point on the wave.Remember one complete wave includes a peak and a trough.

Thetime periodof a wave is thetime it takes for one complete wave.

Thefrequencyof a wave is thenumber of waves that travels past a point in one second. Frequency is measured in Hertz (Hz). 1 Hz = 1 wave per second.

There is a simple relationship between frequency and time period. The lower the frequency is the longer the time period will be.

Example:

THE WAVE EQUATIONThere is a simple relationship between speed, frequency and wavelength.

You must use the correct units for each value Speed is in metres per second (m/s) Wavelength is in metres (m) Frequency is in hertz (Hz).

All waves obey this wave equation. For example, a wave with a frequency of 100 Hz and a wavelength of 2 m travels at 100 2 = 200 m/s.

01. Make measurements on the diagrams below to find the speed of the waveA. Find the wavelength (in meters) of the wave in the diagram.

B. Find the period of the wave in the diagram below.

C. Calculate the frequency of the wave (in cycles/second, or Hertz).

D. Calculate the speed of this wave.

E. Find the wavelength of a wave of electromagnetic radiation that has a frequency of 6 x 1014 Hz (waves of electromagnetic radiation travel at the speed of 3 x 108 m/s (in a vacuum)).

02. The speed of sound in air is 330 m/s. A note played on an instrument has a frequency of 110 Hz. What is the wavelength of the note?

03. The frequency of a water wave is 2 Hz and it has a wavelength of 0.02 m. What is the speed of the wave?

04. Bill counts 5 waves on a pond in 10 s. The distance between them is 80 cm. What is their speed?05. Lizi reads the back label of her Microwave oven. It says frequency = 2,450MHz. The speed of microwaves is 3.00108m/s.what wavelength are they?06. Paul plays a note of wavelength 25 cm on his synthesiser.He knows the speed of sound is 340m/s in air.What is its frequency?

07. A sound wave has a wavelength of 0.5 meters and a frequency of 680 Hz. What is the speed of this wave?

08. What is the frequency of a water wave that has a speed of 0.4 meter per second and a wavelength of 0.02 meter?

09. A vibrating object with a frequency of 200 Hz produces sound which travels through air at 360 m/s. The number of meters separating the adjacent compressions in the sound wave is

010. A wave is introduced into a thin wire held tight at each end. It has an amplitude of 3.8 cm, a frequency of 51.2 Hz and a distance from a crest to the neighboring trough of 12.8 cm. Determine the period of such a wave.

011. Frieda the fly flaps its wings back and forth 121 times each second. The period of the wing flapping is ____ sec.

012. A tennis coach paces back and forth along the sideline 10 times in 2 minutes. The frequency of her pacing is ________ Hz.

013. Non-digital clocks (which are becoming more rare) have a second hand that rotates around in a regular and repeating fashion. The frequency of rotation of a second hand on a clock is __________ Hz.

014. Olive Udadi accompanies her father to the park for an afternoon of fun. While there, she hops on the swing and begins a motion characterized by a complete back-and-forth cycle every 2 seconds. The frequency of swing is ____________.

015. A common physics lab involves the study of the oscillations of a pendulum. If a pendulum makes 33 complete back-and-forth cycles of vibration in 11 seconds, then its period is ____________.

016. The water waves below are traveling along the surface of the ocean at a speed of 2.5 m/s and splashing periodically against Wilbert's perch. Each adjacent crest is 5 meters apart. The crests splash Wilbert's feet upon reaching his perch. How much time passes between each successive drenching? Answer and explain using complete sentences.

017. Two waves on identical strings have frequencies in a ratio of 2 to 1. If their wave speeds are the same, then how do their wavelengths compare?

018. Mac and Tosh stand 8 meters apart and demonstrate the motion of a transverse wave on a snake. The wave e can be described as having a vertical distance of 32 cm from a trough to a crest, a frequency of 2.4 Hz, and a horizontal distance of 48 cm from a crest to the nearest trough. Determine the amplitude, period, and wavelength and speed of such a wave.

019. Ocean waves are observed to travel along the water surface during a developing storm. A Coast Guard weather station observes that there is a vertical distance from high point to low point of 4.6 meters and a horizontal distance of 8.6 meters between adjacent crests. The waves splash into the station once every 6.2 seconds. Determine the frequency and the speed of these waves.

020. Two boats are anchored 4 meters apart. They bob up and down, returning to the same up position every 3 seconds. When one is up the other is down. There are never any wave crests between the boats. Calculate the speed of the waves.

http://www.physicsclassroom.com/class/waves/u10l2e

Consider the diagram below in order to answer questions #1-2.

021. The wavelength of the wave in the diagram above is given by letter ____________________________

022. The amplitude of the wave in the diagram above is given by letter ____________________________

023. Indicate the interval that represents one full wavelength.

The distance from the crest of one wave to the crest of the next wave is called:The amplitudeThe wavelengthThe frequencyWhat are the units of frequency?m/ssHz3.Which is a correct equation?wave speed = frequency wavelengthwave speed = frequency + wavelengthwave speed = frequency wavelengthWhich statement about the oscillations of light waves is correct?They are parallel to the direction of energy transferThey are perpendicular to the direction of energy transferThey rotate around the direction of energy transfer5.Some types of waves are longitudinal. This means that the oscillations:Are perpendicular to the direction of travel and energy transferAre in the same direction as the direction of travel and energy transferRotate around the direction of travel and energy transfer

http://www.s-cool.co.uk/gcse/physics/properties-of-waves/revise-it/reflection-of-waves

http://www.s-cool.co.uk/gcse/physics/properties-of-waves/revise-it/describing-waves

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/waves/generalwavesrev5.shtml