4-1 Radiant Energy

Waves  Light travels in Waves similar to ocean waves  Light waves are electromagnetic and consist of an electric and magnetic fields oscillating at right angles to each other in the direction of motion.

 Wavelength – distance between crests  Amplitude – height of the wave measured from the origin to its crest or peak  Brightness  Frequency – tells how fast a wave oscillates  The number of times a wave completes an up and down cycle  Measured in cycles per second  s -1 = 1/s = hertz = Hz

 Light moves in space at a constant speed. c = 3.00 x 10 8 m/s  Because of this, there is a relationship between wavelength and frequency.  Shorter the wavelength, the faster the oscillation  c = x  = c/

Practice Problem  Calculate the wavelength of a radio wave with a frequency of 93.1 x 10 6 s -1  = c/ = 3.00 x 10 8 m/s / 93.1 x 10 6 s -1 = 3.22 m

Electromagnetic Spectrum

 We see light in the visible spectrum  Each color that we see has a different wavelengths.  400 nm (violet) – 700 nm ( red)  Visible light is a very small portion of the electromagnetic spectrum.  Much of the spectrum is below and above the Visible portion m – 10 1 m

 Beyond red is the infrared portion. This is also called radiant heat  Used in microwaves, radio waves, tv waves

 Beyond violet is the ultraviolet radiation (UV)  Responsible for sunburns and skin cancer.  X-rays are even shorter in wavelength