Download The Energy of Waves

The Energy of Waves
Light and Sound
The Nature of Waves
• Wave: a periodic disturbance in a solid, liquid, or gas as energy
is transmitted through a medium.
• Examples: waves on the ocean, light waves from the Sun,
microwaves in a microwave oven, etc.
Properties of Waves
• Amplitude: the maximum distance that the particles of a
wave’s medium vibrate from their rest position.
• The Larger the Amplitude = More Energy
Properties of Waves Continued
• Wavelength: the distance from any point on a wave to an
identical point on the next wave.
• Shorter Wavelength = More Energy
Wavelengths and Math
• Frequency: the number of waves produced in a given amount
of time.
• Frequency is expressed in hertz ( Hz)
• Example 2 waves in 10 seconds has the frequency of 2/10 s = 0.2 Hz
• Wave Speed: the speed at which a wave travels through a
medium.
• Wave speed is expressed in (v)
• Wavelength in
, or Lambda
• Frequency is (f)
• Equation: v =
Xf
• Medium: a physical environment in which phenomena occur.
• Solid
• Liquid
• Gas
• Sound must be in a Medium.
• So, no sound in space
• As well as Mechanical Waves
• Water and strings of instruments
This is not accurate!!!
• Death Star Explosion… Play the clip.
Energy Transfer Without
Medium
• Some waves don’t need a medium, such as:
• Visible Light, Microwaves, and TV and Radio
Parts of a Wave
Types of Waves
• Transverse waves: a wave in which the particles of the
medium move perpendicularly to the direction the wave is
traveling.
Types of Waves Continued
• Longitudinal wave: a wave in which the particles of the
medium vibrate parallel to the direction of the wave motion
Types of Waves…
• Sound Waves
• A longitudinal wave that is caused by vibrations and that travels
through a material medium
• Medium at which sound travels:
•
•
•
•
Water
Air
Glass
Metal, etc.
Properties of Sound
Speed of Sound in Different Media
Medium
Speed (m/s)
Air (0°C)
331
Air (20°C)
343
Air (100°C)
366
Water (20°C)
1,482
Steel (20°C)
5,200
Sound Continued
• Pitch: a measure of how high or low a sound is perceived to
be, depending on the frequency of the sound wave.
Frequencies
Frequencies Heard by other Animals
Animal
Frequency range (Hz)
Bat
2,000 to 110,000
Porpoise
75 to 150,000
Cat
45 to 64,000
Beluga whale
1,000 to 123,000
Elephant
16 to 12,000
Human
20 to 20,000
Dog
67 to 45,000
Humans have one of the smallest ranges
in the animal kingdom
Loudness and Amplitude
• Loudness: The measure of how well a sound can be heard
• The more energy that is transferred, the louder it is.
• Example: Drum
• Amplitude: Is the largest distance the particles in the wave can
vibrate.
Doppler Effect
• An observed change in the frequency of a wave when the
source or observer is moving.
Light Waves
• Light is an Electromagnetic Wave
• It is a wave that can travel through empty space or matter and
consists of changing electric and magnetic fields.
The Speed of Light
• 365,000 km/s
• 365,000,000 m/s
• 186,000 mi/s
• It takes the Sun’s light a little over 8 minutes to get to Earth
• Sound vs Light
• Sound travels at 343 m/s
• That’s why you see lightning before hearing thunder
Electromagnetic Spectrum
Visible Light Spectrum
• Red, Orange, Yellow, Green, Blue, Indigo, and Violet
• The Wavelengths go from larger to smaller (left to right)
• The visible light from the Sun is White Light
• A combination of all the colors
Interactions of Light Waves
• Reflection: the bouncing back of a ray of light,
sound, or heat when the ray hits a surface that is
does not go through.
• Absorption: in optics, the transfer of light energy
to particles of matter
• Scattering: an interaction of light with matter
that causes light to change its energy, direction
of motion, or both.
• Refraction: the bending of a wave as the wave
passes between two substances in which the
speed of the wave differs
• Refraction and Optical Illusions
• Diffraction: a change in the direction of a wave finds an
obstacle or an edge, such as an opening.
•
Light and Color
• Transmission: the passing of light or other forms
of energy through matter
Why are strawberries red?
• Humans see different wavelengths of light as different colors.
• Some colors reflect and others are absorbed off the object.
Mixing Colors of Light
• Pigment: a substance that gives another substance or a
mixture its color
• Example dye for a shirt that gives it its color.