physical science 9 chapter 13: electromagnetic...
TRANSCRIPT
Physical Science 9���Chapter 13: Electromagnetic
Waves ���Chapter 14: Light���
Chapter 15: Mirrors and Lenses
Section 13.1: …Electromagnetic Waves Section 13.2: The Electromagnetic Spectrum
Electromagnetic Waves --Electromagnetic waves consist of electric!
and magnetic fields vibrating at right angles!to each other.!
--Electromagnetic waves are produced by!vibrating electric charges.!
--Electromagnetic waves used in radio and!TV broadcasts are produced by electric!currents produced in the antennas.!
--See animation of electromagnetic waves.!(HP 06, Ch 13, 70120html)!
Speed of Electromagnetic Waves --Electromagnetic waves can travel through!
a vacuum at a speed of 3.0 x 108 m/s!(186,000 mi/sec). !
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c = f ∗λorc = ν *λ
--The speed of electromagnetic waves is given by:!
--Light travels from the Sun to the Earth in!about 8 1/3 minutes.!
--Light can travel about 7 1/2 times around!the Earth in one second!!!!
--According to Einstein’s Theories of Relativity,!nothing can travel faster than light; the speed!of light is the ultimate speed limit in the!universe.!
The Electromagnetic Spectrum --The electromagnetic spectrum consists of!1. radio waves! 2. microwaves!
3. infrared waves! 4. visible light waves!
5. ultraviolet waves! 6. x-rays!
7. gamma rays!
--The parts of the electromagnetic spectrum!vary in their frequency, wavelength, and energy.!
--Electromagnetic waves with a short wavelength!have a high frequency and a high energy.!
Examples: x-rays and gamma rays!
--Electromagnetic waves with a long wavelength!have a low frequency and a low energy.!
Example: radio waves!
The Electromagnetic Spectrum
The Electromagnetic Spectrum
Calculations with the Speed of Light
Example: What is the speed of light in a vacuum!if a wave with a frequency of 700 nm has a!frequency of 4.3 x 1014 Hz?!
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λ = 700 nm x 1 m109 nm
= 7.0 x 10-7 m
or
λ = 700 nm x 10-9 m1 nm
= 7.0 x 10-7 m
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c = f × λ
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c = (4.3 x 1014 Hz) × (7.0 × 10-7 m)
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c = 3.01 x 108 ms
Example 2: What is the wavelength of a radio!wave whose frequency is 1.0 x 108 Hz?!
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c = f x λ
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λ = cf
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λ = 3.0 x 108 m
s1.0 x 108 Hz
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λ = 3.0 m