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# Waves - PowerPoint PPT Presentation

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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### Waves

http://ngsir.netfirms.com/

• Rhythmic disturbance that carries energy through matter or space.

• Mechanical Waves

• Require a medium

• Electromagnetic Waves

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

• Transverse

• Vibration is perpendicular to the direction of wave movement

• Longitudinal

• Vibration is parallel to wave motion.

• Surface Waves

• Have characteristics of both

• Amplitude

• Displacement from position of rest

• Depends on how wave is generated

• More “work” gives a larger amplitude

• Wavelength

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

• Represented with λ

• Period

• The time it takes for one wavelength to pass

• Represented with T, measured in seconds

• Frequency

• Number of oscillations the wave makes each second.

• Measured in hertz (Hz)

• 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

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

• Constructive Interference – amplitudes in same direction; add together

• When waves’ reflections interfere constructively with each other.

• Node – doesn’t move at all

• Antinode – sees the largest displacement

Resonance

• 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

Pitch

• Related to the frequency of the vibration

Doppler Shift

• 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.

• 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.

http://www.olympusmicro.com/primer/lightandcolor/polarization.htmlhttp://www.olympusmicro.com/primer/lightandcolor/polarization.html

http://www.sunglasswarehouse.com/thesunauthority/polarization-test

Polarization

Reflection

• Law of Reflection

• Angle of Incidence equals Angle of Reflection

Reflectionhttp://www.olympusmicro.com/primer/lightandcolor/polarization.html

• Regular Reflection

• Smooth Surface

Reflectionhttp://www.olympusmicro.com/primer/lightandcolor/polarization.html

• Diffuse Reflection

• Rough Surface

• Light is scattered

Refraction

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

• The angle that a refracted wave makes with the normal

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

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

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

Diffraction

• Bending of a wave around an obstacle

• The separation of light into its colors

Why is the Sky Blue?http://homepage.usask.ca/~dln136/refraction/pages/first_intro.html

• Object – the source of diverging light waves

• Image – the light that is viewed

• Smooth flat surface

• 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.

• Curved inward

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

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

• Remember: Angle of incidence equals angle of reflection!

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

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

• 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.

• 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

glass)

• Translucent – light goes

through, but is scattered so

image is not easily seen

(frosted glass)

• Opaque – no light goes

through