Exercises

1. (a) Why are fluorescent tubes usually cylindrical ?
   (b)What are the hazards invloved in the disposal of fluorescent tubes ?
2. In contrast to incandescent bulbs and fluorescent lamps, light sticks use no electric power source. How do they produce light? (Hint: see Ref.[4])
3. ``Black light" are used in several places to reveal invisible images or writing. How do they work ?
4. Some detergents claim to produce ``whiter than white'' clothes on washing. How do they work?
5. Can you estimate the temperature of the glowing charcoal in your barbeque pit ?
6. (a) What advantage and/or protection can a good pair of sunglasses provide ?
   (b)What are some of the dangers of using a cheap pair of sunglasses?
   (c) How do Polaroid sunglasses work?
   (d) Can one produce "Polaroid" sound filters? Why not?
   (e) Try out the simulations in ref.[6] and link with what you have learned.
7. (a) Why is UV light capable of producing skin damage but visible light not?
   (b) Why do some people apply sunscreen lotion when they are out in strong sunlight for long periods?
   (c) Why is it that wearing sunglasses while at the beach might increase someones chances of getting sunburn ? Why is sunburnt skin reddish ?
   (d) Why are some drugs packaged in amber-coloured containers ?
   (e) So is there any use of exposure to sunlight ?
   (Hint : see Ref.[13]).
8. (a) Where does the energy of an intense laser beam come from ?
   (b) What are some of the applications of lasers ?
   (c) What different types of lasing mediums are there ?
   (d) What kind of laser would you use to cut through steel ?
   (e) Are supermarket laser scanners and laser pointers dangerous in any way ?
   (Hint: See Ref.[10]).
9. (a) What are the advantages of optical fibers compared to conventional copper wires for communications ?
   (b) What are some other applications of optical fibers?
   (Hint: See Ref.[11]).
10. Optional:
    (a)If thunder is heard two seconds after lightning is seen, how far away did the event originate?
    (b)Device a rule-of-thumb to determine the approximate location of a lightning strike (You may take the speed of sound to be 340m/s).
    (c) Why do trees often explode when struck by lightning ?
11. Optional: Adaptive optics is a method of getting better resolution of stars by cancelling the effects of the atmosphere. Read about the latest exciting developments in Ref.[8].
12. Optional: Read pp 203-212 of Ref.[14] to understand the factors that led to the design of the Petronas towers.