PHYS 1901 Lecture Notes - Lecture 8: Microwave Oven, Incandescent Light Bulb, Astronomy Class
1 Jun 2020
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Visible light: through a prism white light splits into its component colors red to violet, different colors of light correspond to different wavelengths, blue light has a shorter wavelength than red light. Different ranges have different names: long wavelength, low frequency, radio waves, short wavelength, high frequency, gamma rays. Fm radio: frequency 88-108 mhz (1 mh= 106hz, convert to wavelength 2. 8=3. 4m, long wavelengths short enough to be blocked by buildings and hills, diffraction helps, best reception direct line of sight to transmitter. Am radio: frequency 54-1250 khz (1khz= 103 hz, wavelength 182-556m, longer wavelengths, few objects large enough to block them. Wavelength range: 1mm-1m: radio waves with short wavelengths. In a microwave oven radio waves tuned to excite water molecules in food. Water (80% in food) becomes hot and heats other molecules. Screen in front of oven, holes large enough to allow visible light to pass through but small enough to block most microwaves.
