(4) Strong nuclear force force that binds protons & neutrons Forces of Nature Newton's Laws of Motion Inverse square law of forces Fundamental forces (4) (3) Weak nuclear force Example: β-decay or top bottom quark (4) Strong nuclear force force that binds protons & neutrons in atomic nuclei (1) Gravitational force Example: falling apple (2) Electromagnetic force horseshoe magnet

Waves A wave is a pattern of motion that can carry energy without carrying matter along with it Wavelength = distance between two wave peaks Frequency = number of times per second that a wave vibrates up and down wave speed = wavelength x frequency wave speed = l * f

Electromagnetic Spectrum Progression of frequency or wavelength Radio, millimeter, sub-millimeter, microwave, infrared, optical, ultraviolet, X-ray, gamma rays Optical/visible white light spectrum (rainbow colors): Red Orange Yellow Green Blue Indigo Violet [Order of decreasing wavelength, increasing frequency]

Doppler Shift Demonstrator Check out the interactive website: http://astro.unl.edu/classaction/animations/light/dopplershift.html Click the “start emission” button, check the “show paths” button, and then click and drag the source of electromagnetic radiation “S” or the observer “O” and observe what happens. Compare the waves of electromagnetic radiation as emitted from the source to the waves as detected by the observer. Any relative motion between the source and observer causes the observer to observe a different frequency and wavelength than emitted by the source. This is known as Doppler shift.

Atmospheric Windows Optical, [sub-millimeter], millimeter, and radio wavelengths Impact on astronomy (and on human evolution!)