1. Unit 11, Section 1

2.  Light can take millions of years to travel to Earth  All electromagnetic radiation travels at the speed of light, which is 300,000 km/s  Electromagnetic waves can carry energy through empty space and matter  Examples: radio waves, microwaves, light, gamma rays, X-rays, and UV (ultraviolet) rays.  All of these together make up the electromagnetic spectrum

3.  Optical Telescopes use light  Reflecting Telescopes use a concave mirror  Refracting Telescopes use a convex lens  Most optical telescopes are in observatories  Space telescopes get clearer pictures because Earth’s atmosphere blurs the pictures Example of a space telescope: Hubble

4.  Radio Telescopes collect radio waves not light, so they can be used 24/7 no matter what the weather is