Electromagnetic Waves Chapter 12

Light Made of photons Part particle and part wave massless particles with concentrated electromagnetic energy Part particle and part wave Wave = electromagnetic wave (transverse) Unlike sound which is called a mechanical wave (longitudinal) Does not require a medium to travel through space

Speed of Light 3.0 x 108 m/s Speed of light > speed of sound Light year Distance light travels in a year

Electromagnetic Waves Electromagnetic spectrum All forms of electromagnetic waves Includes: Visible Light (ROYGBIV) Radio waves UV rays Microwaves Gamma rays Infrared

Just like other waves, Electromagnetic waves follow rules such as: Shorter the wavelength, higher the frequency Longer the wavelength, lower the frequency This is because the speed of light is the same for all forms of electromagnetic radiation

Frequency of electromagnetic radiation is directly proportional to the energy of the radiation Wavelength of electromagnetic radiation is inversely proportional to the energy of the radiation.

Color of Objects The color of objects around us is due to what wavelength of light the object reflects If the object reflects green and absorbs all other colors, the object will look green to us White light (sunlight) is due to all colors being reflected Black light is due to all colors being absorbed

Sunlight Why is the sky blue? Most of the UV light from the sun is absorbed by the ozone layer The rest is scattered by atmospheric particles Violet and blue are scattered the most (reflected) and since our eyes are not sensitive to violet the sky appears blue

Why are sunsets red? When the sun sets, the sunlight reaches us through a longer path through the atmosphere Longer wavelength light is scattered (reflected) in atmosphere, therefore the sky is red (which is the longest wavelength color of visible light)