ASTR 001 Lecture Notes - Lecture 8: Visible Spectrum, Electromagnetic Spectrum, Moe Williams

• School: Pasadena City College
• Department: Astronomy
• Course: ASTR 001
• Professor: Hartman

Document Summary

Almost all knowledge of the universe beyond earth comes from light. Light can tell us about objects in space: temperature, composition, speeds, age, etc. Light moves at 300,000km/s in a vacuum. First measured by romer when observing jupiter"s moons. Light travels at slower speeds in other media (gasses, glass, water) Light is a wave of combined electricity and magnetism, called an electromagnetic wave. Changing electric and magnetic fields create a self-sustaining electromagnetic wave. Frequency (f): number of waves that pass by each second. Period (p): time to complete one cycle. The speed of light, c, is constant. Visible spectrum: small range of wavelength that humans can see. Red light= longest wavelength (/\ ~ 750 nm) Violet light= shortest wavelength (/\ ~ 380 nm) Visible light is just one small part of the electromagnetic spectrum. To the right is increasing wavelength and decreasing frequency. To the left is decreasing wavelength and increasing frequency.