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Waves PowerPoint PPT Presentation

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Waves. http://ngsir.netfirms.com/. Wave. Rhythmic disturbance that carries energy through matter or space. Types of Waves. Mechanical Waves Require a medium Electromagnetic Waves Move because of an electromagnetic force field; don’t need a medium. Types of Mechanical Waves. Transverse

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  • Rhythmic disturbance that carries energy through matter or space.

Types of Waves

  • Mechanical Waves

    • Require a medium

  • Electromagnetic Waves

    • Move because of an electromagnetic force field; don’t need a medium.

Types of Mechanical Waves

  • Transverse

    • Vibration is perpendicular to the direction of wave movement

  • Longitudinal

    • Vibration is parallel to wave motion.

  • Surface Waves

    • Have characteristics of both

Wave Properties

  • Amplitude

    • Displacement from position of rest

    • Depends on how wave is generated

    • More “work” gives a larger amplitude

Wave Properties

  • Wavelength

    • Distance of one wave from similar points (crest to crest or trough to trough)

    • Represented with λ

Parts of Longitudinal Waves

Wave Properties

  • Period

    • The time it takes for one wavelength to pass

    • Represented with T, measured in seconds

Wave Properties

  • Frequency

    • Number of oscillations the wave makes each second.

    • Measured in hertz (Hz)

Wave Properties

  • Speed

    • Depends on the material the wave is traveling through

    • Speed = λf


  • The result of having two waves in the same place at the same time

  • Also known as superposition

  • The waves will either combine or cancel each other out

Types of Interference

  • Destructive Interference – amplitudes are displaced in opposite directions, so they cancel each other out when meeting.

  • Constructive Interference – amplitudes in same direction; add together

Standing Waves

  • When waves’ reflections interfere constructively with each other.

    • Node – doesn’t move at all

    • Antinode – sees the largest displacement


http://www.youtube. com/watch?v=zpUL6sZs6J4



  • the tendency of a system to oscillate with greater amplitude at some frequencies than at others


  • Sound waves

    • Pressure variation transmitted through matter.

    • Speed depends on the material traveling through


  • Depends on the amplitude of the pressure wave.

  • Remember more amplitude = more energy



  • Related to the frequency of the vibration



Doppler Shift

Doppler Effect in Light


  • We refer to light as the part of the electromagnetic spectrum that is visible to our eyes.


Electromagnetic Spectrum

  • Visible light is only one small part of the broad spectrum of electromagnetic waves.


  • What we see as “white light” is actually a combination of all colors at once.

Name that band and album.

Perceiving Colors

  • The color you see on an object is actually being absorbed by the object – what reaches our eye is everything BUT that color.


  • Light (ER) vibrates in two directions. Polarizing filters reduce the motion in one of the directions.






  • Law of Reflection

    • Angle of Incidence equals Angle of Reflection


  • Regular Reflection

    • Smooth Surface


  • Diffuse Reflection

    • Rough Surface

    • Light is scattered




  • The bending of light waves at a boundary between two different media

Angle of Refraction

  • The angle that a refracted wave makes with the normal

Critical Angle

  • The incident angle that will cause a reflected ray to lie along the boundary of a surface.

Total Internal Reflection

  • Angle at which the ray is reflected back into the medium

Fiber Optic Cable



http://w ww.gcsescience.com/pwav44.htm


  • Bending of a wave around an obstacle


  • The separation of light into its colors

Why is the Sky Blue?

Objects vs. Images

  • Object – the source of diverging light waves

  • Image – the light that is viewed

Plane Mirror

  • Smooth flat surface

Virtual Image

  • The point that the eye interprets the light rays as having come from

  • In a plane mirror, the image is the same size and distance from the mirror as the object is.

Concave Mirrors

  • Curved inward

  • Principle axis – straight line to the surface at the center

Concave Mirrors

  • Focal point – where the parallel rays meet after reflecting.

    • Remember: Angle of incidence equals angle of reflection!

Concave Mirrors

  • Focal length – distance from the focal point to the mirror

  • Real Image – light rays actually converge at that point (not virtual). Projected image.

Concave Mirrors

  • Magnification – the ratio of the size of the image to the size of the object.

  • Inside the focal point – forms enlarged virtual images.

  • Outside the focal point – forms smaller virtual images that are upside-down.

Convex Mirrors

  • Spherical – reflects light from the outer surface.

  • Rays always diverge – no real images produced.


  • Made of a transparent material with a refractive index greater than air.

  • Remember:

    • Transparent – light goes

      through uninterrupted (clear


    • Translucent – light goes

      through, but is scattered so

      image is not easily seen

      (frosted glass)

    • Opaque – no light goes


Convex Lens

  • Thicker at the center than at the edges

    • Also known as converging lens

Concave Lens

  • Thinnest in the center

    • Also known as a diverging lens

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