# COMT 3911 Some Fundamentals. COMT 3912 Fundamentals The Metric System What is a “Wave” Calculations in “Decibels”

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COMT 3911 Some Fundamentals

COMT 3912 Fundamentals The Metric System What is a “Wave” Calculations in “Decibels”

COMT 3913 The Metric System Based on MKS - Meters, Kilograms, Seconds 1 m is about 3 feet 1 kg is about 2.2 pounds

COMT 3914 “Scientific” Notation Large and small numbers are written as a number “around” 1, multiplied by ten raised to the proper power –41,400 = 4.14x10 4 –1,000,000,000,000 = 1x10 12 –0.0000543 = 5.43x10 -5

COMT 3915 Try It 9845 768000000 0.012 0.3 0.0000000004

COMT 3916 And the answers are... 9845 = 9.845x10 3 768000000 = 7.68x10 8 0.012 = 1.2x10 -2 0.3 = 3x10 -1 0.0000000004 = 4x10 -10

COMT 3917 Number Prefixes Prefix designates powers of 10  0.00000110 -6 m0.00110 -3 c0.0110 -2 k100010 3 M100000010 6 G100000000010 9

COMT 3918 Try it Convert 10000m to km Convert 1mm to m Convert 3mm to km Convert 13km to  m

COMT 3919 The Result 10000m = 10km 1mm = 0.001m = 10 -3 m 3mm = 3x10 -6 km 13km = 1.3x10 -10  m

COMT 39110 Some Numbers Speed of light: 3x10 8 m/s or 300,000,000 m/s or 300,000 km/s Mass of the earth: 5.98x10 24 kg Radius of the earth: 6.38x10 6 m Speed of sound in air: 343 m/s

COMT 39111 Waves A wave can be roughly defined as an organized series of disturbances traveling through space or through a medium.

COMT 39112 “Ripples” - Surface Waves

COMT 39113 At a fixed time...

COMT 39114 At one point along the surface

COMT 39115 Measurements Amplitude (A) Wavelength ( ) in meters (with prefix) Number of cycles per second is frequency (f) In 1/sec = Hz

COMT 39116 Types of Waves Sound - pressure disturbance in a medium (air, water, etc.) Surface - disturbance in the “normal” position of the surface Electromagnetic - alternating electric and magnetic disturbances in a medium or in a vacuum.

COMT 39117 For all waves: The speed of the wave is equal to the product of the wavelength and the frequency.

COMT 39118 Some Examples Speed of light: 3x10 8 m/s Find the wavelength for each case –AC Current: 60Hz –FM Radio: 90MHz –Ka Band Satellite: 20GHz –Ultraviolet Light: 10 15 Hz The speed of the wave is equal to the product of the wavelength and the frequency.

COMT 39119 Some Examples Speed of light: 3x10 8 m/s Find the wavelength for each case –AC Current: 60Hz = 5000km –FM Radio: 90MHz = 3.33m –Ka Band Satellite: 20GHz = 15mm –Ultraviolet Light: 10 15 Hz = 3x10 -7 m The speed of the wave is equal to the product of the wavelength and the frequency.

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