| A | B |
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| Blueshift | The wavelengths of electromagnetic radiation from an approaching source are compressed= Because each successive wave is emitted from a position slightly closer, you see a shorter wavelength than you would see if the source were stationary= All colors in the spectrum of an approaching source, such as a star, are therefore shifted toward the short-wavelength (blue) end of the spectrum, regardless of its distance |
| Doppler Shift | A blueshift or a redshift is also called a Doppler shift= THe amount of Doppler shift varies directly with approaching or receding speed: When the speeds are small compared to the speed of light, an object approaching 2x as fast as another has all its colors (or wavelengths) blueshifted 2x as much as does the slower-moving object= Converselt, an object moving away 2x as fast as another object has its colors redshifted 2x as much as the slower moving object |
| Electromagnetic Radiation | Energy that has properties of both particles, called photons, and waves |
| Photon | Light travels as waves enclosed in discrete packed called photons |
| Redshift | Electromagnetic waves from a receding source are stretched out= You see a longer wavelength than you would see if the source were stationary= All the colors in the spectrum of a receding source, regardless of its distance, are shifted toward the longer-wavelength (red) end of the spectrum |
| Reflection | The phenomenon of a propagating wave being thrown back from a surface |
| Refracting Telescope (refractor) | Telescopes that collect light through lenses |
| Refraction | Change in direction as light travels from one medium into another |
| Very-Long-Baseline Interferometry (VLBI) | Is the linking of radio telescopes separated by many kilometers thus producing images that are much sharper and clearer than even those from optical telescopes |
| Wavelength | The distance between two corresponding points on any two consecutive waves |
