1. What is lightning?
2. What causes thunder?
3. Why do we see lightning first and hear thunder after a delay?
4. Sound travels through air at a speed of _____________ metres per second.
5. If a lightning flashed 1 kilometer away and we saw it immediately, how long would it take for the sound of thunder to reach us?
6. Normally, a human voice can be heard over a distance of ________ metres in still air.
7. How can we conclude that light travels in straight lines by observing shadows?
8. What is umbra & penumbra?
9. Two conditions (of the light source) that result in sharper shadows.
10. Can sound travel through space? Why?
11. How can two astronauts in the moon speak to each other?
12. Does sound obey the Law of Reflection?
13. Why do we sound better when we sing in the shower?
14. Why does a crowd of people in a carpeted room seem to make less noise than in a room with a hard floor?
15. Solar and lunar eclipses are caused by shadows. How does solar and lunar eclipse occur?