Chapter 14 Light and Reflection

Light is a form of electromagnetic radiation

All electromagnetic radiation travels at c = 3.00 x 108 m/s c = f l constant

Radio Waves longest wavelength l ˃ 0.3 m smallest frequency f ˂ 109 Hz Used to transmit radio and tv signals

Microwaves wavelength 0.3m ˃ l ˃ 1 x 10-3m frequency 1 x 109 Hz ˂ f ˂ 3 x 1011 Hz Used in radar, ovens and communication (cell phones)

Infrared wavelength 1 x 10-3 m ˃ l ˃ 700 nm frequency 3 x 1011 Hz ˂ f ˂ 4.3 x 1014 Hz ~heat~

Visible Light wavelength 700 nm (red) ˃ l ˃ 400 nm (violet) frequency 4.3 x 1014 Hz ˂ f ˂ 7.5 x 1014 Hz

Ultraviolet (UV) light wavelength 400 nm ˃ l ˃ 60 nm frequency 7.5 x 1014 Hz ˂ f ˂ 5 x 1015 Hz Causes tanning and skin cancer

X rays wavelength 60 nm ˃ l ˃ 10-4 nm frequency 5 x 1015 Hz ˂ f ˂ 3 x 1021 Hz

Gamma rays Used to treat cancer shortest wavelength 0.1 nm ˃ l ˃ 10-5 nm highest frequency 3 x 1018 Hz ˂ f ˂ 3 x 1022 Hz Used to treat cancer

Light is an “inverse square” function, brightness decreases by the square of the distance. Double the distance will be 1/4th as bright

Reflection Light can have diffuse or specular (regular) reflection

The angle of incidence = the angle of reflection

Image distance = Object distance

Images can be real or virtual Real images can be projected

Concave Mirrors C, center of curvature F, focal point Principal axis

Mirror Equation 1/p + 1/q = 1/f object distance focal length image distance

Magnification Equation M = h’/h = -q/p object distance image height image distance object height + M upright virtual -M inverted real