Forces of Nature

• Newton's Laws of Motion

• Inverse square law of forces

• Fundamental forces (4)

(1) Gravitational force Example: falling apple

(2) Electromagnetic force Example: horseshoe magnet

(3) Weak nuclear force Example: β-decay or top bottom quark

(4) Strong nuclear force Example: force that binds protons & neutrons in atomic nuclei

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 = * 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!)