14-1 characteristics of light 1.Identify the components of the electromagnetic spectrum. 2.Calculate the frequency or wavelength of electromagnetic radiation 3.Recognize that light has finite speed. 4.Describe how the brightness of a light source is affected by distance.

The Electromagnetic spectra Electromagnetic waves are TRANSVERSE waves which are capable of traveling through a vacuum. Electromagnetic waves are produced by a vibrating electric charges, they consist of both an electric and a magnetic field at right angles to each other. The alternating electric field creates alternating magnetic field, and the alternating magnetic field creating alternating electric field.

EM Wave Types An EM Wave’s type depends on its frequency/wavelength Wavelength (m) Freq (Hz) Temperature of bodies emitting the wavelength 1 K100 K10000 K10 million K About the size of… Building Human Honey Bee PinpointProtozoanMolecules Atoms Atomic Nuclei RadioMicrowaveInfraredVisibleUltravioletX-rayGamma Ray All objects emit EM radiation

Visible Light Spectrum The visible light – the very narrow band of wavelengths in the spectrum consists of wavelengths which range from approximately 700 nm to approximately 400 nm. This narrow band of visible light is affectionately known as ROYGBIV. Each individual wavelength within the spectrum of visible light wavelengths is representative of a particular color...\..\RealPlayer Downloads\The Electromagnetic Spectrum-Visible light.flv

All electromagnetic waves, including light, travel at the same speed: 3 x 10 8 m/s in air or vacuum. Radio waves are electromagnetic waves. Radio waves not sound waves

Example #1 Radio waves and gamma rays traveling in space have the same 1.frequency 2.wavelength 3.period 4.speed

Example #2 In a vacuum, all electromagnetic waves have the same 1.wavelength 2.frequency 3.speed 4.amplitude

Example #3 Compared to the speed of microwaves in a vacuum, the speed of x-rays in a vacuum is 1.less 2.greater 3.the same

Class work – today’s date 1.Radio wave A has a wavelength of 10. meters, and radio wave B has a wavelength of 12 meters. Compared to the speed of radio wave A in air, radio wave B’s speed in air is a.lower b.the same c.higher

2.What is the wavelength of your favorite radio station? 3.To the nearest order of magnitude, how many times greater than the speed of sound is the speed of light? 4.A typical microwave oven produces radiation at a frequency of 1.0x10 10 hertz. What is the wavelength of this microwave radiation? 5.The constellation of Orion is a highly recognizable arrangement of stars. There are two very distinct stars in this constellation, Betelgeuse which is a red star and Rigel which is a bluish star. The color red has a wavelength of about 750 nm and the color blue has a wavelength of about 400 nm. a. Which color has the higher frequency? b. Which of the two stars is hotter? Betelgeuse or Rigel?

6.An EM wave is traveling through outer space with a frequency of 8.0 x hertz. a. What is the wavelength of this wave? b. What type of wave is this? 7.Listed below are the properties of several EM Waves. State whether the property given is a wavelength or frequency, then state which type of EM Wave it is. a hertz __________________ _________________ b. 5.0 x meter _________________ _________________ c. 3.0 x hertz _____________ ____________________ d. 4.5 x hertz _________________ _________________ e. 200 meters _________________ ____________________

8.What type of electromagnetic radiation is a wave with a _____? o wavelength of... (a) 3.5 x 10 3 meters (b) 4.5 x meters (c) 2.0 x meters (d) 6.0 meters 9.Electromagnetic waves can be produced by which of the following? Which would produce a mechanical wave? a.A plastic slinky vibrating back and forth b.An electron oscillating back and forth c.A neutron oscillating back and forth d.A string with a single disturbance moving through it e.A positively charged sphere vibrating back and forth o frequency of… (a) 3.0 x 10 6 hertz (b) 2.2 x hertz (c) 1.5 x hertz (d) 5.5 x hertz

10.Consider the electromagnetic spectrum as you answer these three questions. a.Which region of the electromagnetic spectrum has the highest frequency? b.Which region of the electromagnetic spectrum has the longest wavelength? c. Which region of the electromagnetic spectrum will travel with the fastest speed?

Huygen’s Principle A wave front can be divided into point sources. Each point sources produces a circular secondary wave, or wavelet. These wavelets lines up next to one another and produce a new wave front.

Ray approximation of waves WAVE RAY – a line perpendicular to wave’s front that shows the direction of a wave’s travel. λ