Waves S Caesar Physics

Objectives In this PowerPoint the students will learn: The properties of a wave Behavior of Waves Differentiate elastic & electromagnetic waves How to calculate the period, frequency, and wave length of a wave.

STANDARDS –SP4 SP4 Description: SP4 Students will analyze the properties and applications of waves. Elements: a. Explain the processes that results in the production and energy transfer of electromagnetic waves.

Mechanical Waves A mechanical wave is a physical disturbance in an elastic medium. Consider a stone dropped into a lake. Energy is transferred from stone to floating log, but only the disturbance travels. Actual motion of any individual water particle is small. Energy propagation via such a disturbance is known as mechanical wave motion.

What are electromagnetic waves? How electromagnetic waves are formed How electric charges produce electromagnetic waves Properties of electromagnetic waves

Electromagnetic Waves… Do not need matter to transfer energy. Are made by vibrating electric charges and can travel through space by transferring energy between vibrating electric and magnetic fields.

This page was copied from Nick Strobel's Astronomy Notes This page was copied from Nick Strobel's Astronomy Notes. Go to his site at www.astronomynotes.com for the updated and corrected version.

Making Electromagnetic Waves The electric and magnetic fields vibrate at right angles to the direction the wave travels so it is a transverse wave.

Electromagnetic Waves These waves do not need matter to travel. Difference between the different waves is wave length EM spectrum illustrates the differences

Electromagnetic Waves How they are formed Kind of wave Sometimes behave as

Transverse with alternating electric and magnetic fields Waves or as Electromagnetic Waves How they are formed Waves made by vibrating electric and magnetic fields cthat can travel through space where there is no matter Kind of wave Transverse with alternating electric and magnetic fields Sometimes behave as Waves or as Particles (photons)

WAVES How are mechanical( elastic) waves different from electromagnetic waves ? Differentiate them in terms of definition, their properties, examples

Mechanical Wave

Differentiate Elastic Example: Water waves Sound waves Waves on a spring or string Mechanical (Elastic) waves need a medium to travel Mechanical waves transport energy and not material Electromagnetic Example Microwave X-ray, Gamma ray Light waves, UV rays Do not need a medium to travel It travels with very high speed Can be described by their wavelength, energy, and frequency

Cont’d Requires initial energy input be created Mechanical waves cause displacement of the matter through which the wave is traveling Mechanical waves vibrations can put air molecules in motion Very low energy and frequency Big wavelength Remember that energy gets transferred and not materials Electromagnetic waves cause no displacement of matter and can transfer energy in the absence of matter Do not need to take place in any media vibrations Very high energy and high frequency Electromagnetic vibrations do not put our molecules in motion

Types of Waves Mechanical Waves Electromagnetic Waves A wave is a method of transferring energy from one place to another without transferring matter. Mechanical waves are those that require a medium for their transfer and include water waves, sound waves and waves in stretched strings. Electromagnetic waves consist of varying electric and magnetic fields. The two fields are perpendicular to each other and to the direction of travel of the wave. Each vibrates with high frequency -

Objectives In this PowerPoint the students will learn: Demonstrate your understanding of transverse and longitudinal waves. Define, relate and apply the concepts of frequency, wavelength, and wave speed. Solve problems related to them.

A Transverse Wave In a transverse wave, the vibration of the individual particles of the medium is perpendicular to the direction of wave propagation. Motion of particles Motion of wave

Longitudinal Waves In a longitudinal wave, the vibration of the individual particles is parallel to the direction of wave propagation. v Motion of wave Motion of particles

Production of a Longitudinal Wave An oscillating pendulum produces condensations and rarefactions that travel down the spring. The wave length l is the distance between adjacent condensations or rarefactions.

Sound Sound is produced when an object vibrates. When an object vibrates it exerts a force on the surrounding Sound is a mechanical wave (requires a medium to travel and they are compression wave (molecules colliding). The medium sound travels through are of Air. Loudness of a sound is recorded in decibels As a sound gets louder, the amplitude of the wave increases

Water Waves An ocean wave is a combi-nation of transverse and longitudinal. The individual particles move in ellipses as the wave disturbance moves toward the shore.

What is a wave? A wave is a disturbance which moves through a medium. Water waves and sound waves are examples of mechanical waves. Light waves are not considered mechanical waves. They are electromagnetic in nature.

What is an amplitude? Amplitude: the height of the wave, measured in meters.

What are frequency waves? Frequency: the number of complete waves that pass a point in one second, measured in inverse seconds, or Hertz (Hz).

What are transverse waves? Speed: the horizontal speed of a point on a wave as it propagates, measured in meters / second. Speed of wave, v = frequency

Terminology Amplitude: Height of Wave (m) Wave Length: distance from one wave top, or crest, to the immediate next. (m) Phase Shift: how far to the left or right the wave slides. (m) Frequency: refers to how many waves are made per time interval. This is usually described as how many waves are made per second, or as cycles per second. (hz) Crest: top most part of the wave Trough: bottom most part of the wave Period: the time needed to repeat one complete cycle of motion.

Frequency and Wavelength Transverse Waves (cont.) Frequency and Wavelength As frequency increases wavelength decreases As frequency decreases wavelength increases

What is wavelength? Wavelength: the distance between adjacent crests, measured in meters.

Velocity and Wave Frequency. The period T is the time to move a distance of one wavelength. Therefore, the wave speed is: The frequency f is in s-1 or hertz (Hz). The velocity of any wave is the product of the frequency and the wavelength:

Problem #1 What is the speed of a periodic wave disturbance that has a frequency of 3.5 Hz and a wavelength of 0.7 m? Given f= 3.5 Hz & V= f x V=

Problem #1 What is the speed of a periodic wave disturbance that has a frequency of 3.5 Hz and a wavelength of 0.7 m? V= f x V= 3.5 x 0.7= 2.45 m/s

Example 2: An electromagnetic vibrator sends waves down a string Example 2: An electromagnetic vibrator sends waves down a string. The vibrator makes 600 complete cycles in 5 s. For one complete vibration, the wave moves a distance of 20 cm. What are the frequency, wavelength, and velocity of the wave? f = 120 Hz v = fl The distance moved during a time of one cycle is the wavelength; therefore: v = (120 Hz)(0.02 m) l = 0.020 m v = 2.40 m/s

Problem #2 An ocean wave has a length of 12.0 m. A wave passes a fixed location every 3.0 s. What is the speed of the wave? Given d= 12.0 m t= 3.0 s v= d / t v= (12/3)= 4.0 m/s

Problem #2 An ocean wave has a length of 155.0 m. A wave passes a fixed location every 9.0 s. What is the speed of the wave? v= d / t V=