1. Do radio waves travel at the speed of sound, at the speed of light, or at some speed in between? 2. What determines whether a material is transparent or opaque? 3. You can get a sunburn on a cloudy...

1. Do radio waves travel at the speed of sound, at the speed of light, or at some speed in between?

2. What determines whether a material is transparent or opaque?

3. You can get a sunburn on a cloudy day, but you can’t get a sunburn even on a sunny day if you are behind glass. Explain.