What is a wave? A wiggle through space and time a wave is a disturbance that travels through a medium from one location to another. a wave is the motion of a disturbance

Period The time of a back and forth swing. Period

Waves Electromagnetic-does not requires a medium Moreno Waves Electromagnetic-does not requires a medium Mechanical-requires a medium Radio Waves Microwaves Longitudinal Transverse Infrared rays Visible Light Ultraviolet rays X-rays Gamma rays

Basic Properties of Waves Amplitude Wavelength Frequency Speed

Wavelength Amplitude Wavelength

Anatomy of a Wave wavelength The distance between two consecutive similar points (in this case two crests) is called the wavelength. This is the length of the wave pulse. Between what other points is can a wavelength be measured?

Wavelength

Anatomy of a Wave Amplitude The distance between the dashed line and point A is called the Amplitude of the wave.\ This is the maximum displacement that the wave moves away from its equilibrium.

Interference The result of superposition of two or more waves.

Interference Constructive interference occurs whenever two waves combine to make a wave with a larger amplitude. Destructive interference when the amplitudes of two waves combine producing a smaller amplitude.

Interference Constructive Interference – wave displacements are in the same direction.

Interference Destructive Interference – the high part of one fills in the lower part of another. Two pulses with equal but opposite amplitudes.

TAKS Released Question Diagram 1 represents a wave. Diagram 2 represents the composite wave formed when a second wave interferes with the original wave. Which of the following best represents the second wave? TAKS Released Question

Anatomy of a Wave In our wave here the dashed line represents the equilibrium position. Once the medium is disturbed, it moves away from this position and then returns to it

Crest Crest Trough Trough

Anatomy of a Wave crest The points A and F are called the CRESTS of the wave. This is the point where the wave exhibits the maximum amount of positive or upwards displacement

Anatomy of a Wave trough The points D and I are called the TROUGHS of the wave. These are the points where the wave exhibits its maximum negative or downward displacement.

Longitudinal Wave The wave we see here is a longitudinal wave. The medium particles vibrate parallel to the motion of the pulse. This is the same type of wave that we use to transfer sound. Can you figure out how?? show tuning fork demo

Longitudinal Waves The particles move along the direction of the wave rather than at right angles to it.

Transverse Waves Transverse waves occur when we wiggle the slinky back and forth. They also occur when the source disturbance follows a periodic motion. A spring or a pendulum can accomplish this. The wave formed here is a SINE wave. http://webphysics.davidson.edu/course_material/py130/demo/illustration16_2.html

Transverse waves A second type of wave is a transverse wave. We said in a longitudinal wave the pulse travels in a direction parallel to the disturbance. In a transverse wave the pulse travels perpendicular to the disturbance.

Transverse Waves The differences between the two can be seen

Transverse Waves to direction of travel of wave. Wave in which disturbance is perpendicular to direction of travel of wave.

Natural Frequency When any object composed of an elastic material is disturbed, it vibrates at its own set of frequencies, which together form its special sound. The natural frequency of the smaller bell is higher than that of the big bell, and it rings at a higher pitch.

Frequency of the vibration produced Strength of the plucking force TAKS Released Question The pitch of a sound made by plucking a guitar string is determined by the — Frequency of the vibration produced Strength of the plucking force Distance between the strings Shape of the guitar body

Resonance Most objects have a natural frequency of vibration. Resonance occurs when vibrations traveling through an object match the object’s natural frequency and results in dramatic increase of amplitude. An object that is vibrating at its natural frequency absorbs energy from the objects that vibrate at the same frequency. Occurs in music.

Interference The Doppler effect Resonance Standing waves TAKS Released Question One tuning fork is struck and placed next to an identical fork. The two forks do not touch. The second tuning fork starts to vibrate because of — Interference The Doppler effect Resonance Standing waves

Echo formation Diffraction Resonance Specular reflection TAKS Released Question An empty cup was tightly covered with plastic wrap, and a few grains of salt were sprinkled on top of the plastic. When a tuning fork was struck and placed slightly above the plastic wrap, the salt began to move. Which characteristic of waves does the movement of the salt best demonstrate? Echo formation Diffraction Resonance Specular reflection

Moreno Polarization Light waves can vibrate in many directions. Those that are vibrating in one direction -- in a single plane such as up and down -- are called polarized light.

Refraction of Light Refraction – Bending of light due to a change in speed. Index of Refraction – Amount by which a material refracts light. Prisms – Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors.

Refraction (Cont.)

Reflection When an object or wave hits a surface through which it cannot pass, it bounces back.

Echolocation Reflection – high frequency sound waves that bounce off of objects.

Laser Light Striking a DVD TAKS Released Question When a DVD is read, laser light touches the DVD surface and is then measured at location A. What allows light to return to location A after striking the DVD surface? Conduction Refraction Magnification Reflection Laser Light Striking a DVD