Physics homework XII-25th Feb Sunday

1. What is doppler effect? Find an expression for the change in apparent frequency when the source passes by the stationary observer.
2. Whistle of an approaching train is shriller. Why?
3. A tunning fork has two prongs. Why?
4. In which medium is the angle of polarization greater, rarer or denser?
5. Define a.c.power. Derive an expression for it. Also define power factor.
6. What is wattless current?
7. What do you mean by radiation hazard? What are its safety measures?
8. Give a brief account on "Energy sources of Nepal".
9. Explain the term artificial radio isotopes.
10. What do you mean by dark energy and dark matter?

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