1. Light
Ch 27.1 – 27.3 & 28.1 – 28.2 & 28.8 – 28.9

2. 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

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

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

6. 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

7. 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.

8. 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

9. 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

10. 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)