The spectrum of electromagnetic radiation . The speed of light . Wavelength and frequency . Graphs of intensity vs. wavelength . How light is made from random motions .
Light is made of photons .
How light is made from ordered motion of electrons in atoms and molecules . Measuring the spectrum of light from the Sun tells us what the Sun is made of . The wavelength of light emitted from a moving object is shifted. The apparent brightness of an astronomical object depends on its distance from us.