Waves
description
Transcript of Waves
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– 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)
f = 1T
Wave Properties
• Speed– Depends on the material the wave is traveling through– Speed = λf
Interference
• 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
Resonance• the tendency of a system to oscillate with
greater amplitude at some frequencies than at others
http://www.youtube.com/watch?v=hiHOqMOJTH4http://www.youtube. com/watch?v=zpUL6sZs6J4http://www.youtube.com/watch?v=nO0bSSXmr1A
Sound
• Sound waves– Pressure variation transmitted through matter.– Speed depends on the material traveling through
Loudness
• Depends on the amplitude of the pressure wave.• Remember more amplitude = more energy
Pitch
• Related to the frequency of the vibration
http://www.youtube.com/watch?v=ngk-ECb8ccQ
Doppler Shift
http://www.youtube.com/watch?v=Y5KaeCZ_AaYhttp://www.youtube.com/watch?v=Djz_rtnXSfY
Doppler Effect in Light
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.
http://www.youtube.com/watch?v=UzI1z0u_700
Light
• 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.
Polarization
• Light (ER) vibrates in two directions. Polarizing filters reduce the motion in one of the directions.
Polarization
http://www.olympusmicro.com/primer/lightandcolor/polarization.htmlhttp://www.sunglasswarehouse.com/thesunauthority/polarization-test
Reflection
• Law of Reflection– Angle of Incidence equals Angle of Reflection
http://www.youtube.com/watch?v=LTWHxZ6Jvjs
Reflection
• Regular Reflection– Smooth Surface
Reflection
• Diffuse Reflection– Rough Surface– Light is scattered
Refraction
• The bending of light waves at a boundary between two different media
http://homepage.usask.ca/~dln136/refraction/pages/first_intro.htmlhttp://www.youtube.com/watch?v=Bf1k9-4bb4w
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
Mirages
Diffraction
• Bending of a wave around an obstacle
http://www.falstad.com/ripple/http://w ww.gcsescience.com/pwav44.htm
Dispersion
• 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.
Lenses
• 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
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