Questions from Modern Physics

Q: A 45°-45°-90° prism is immersed in water

A 45°-45°-90° prism is immersed in water. A ray of light is incident normally on one of its shorter faces. What is the minimum index of refraction that the prism must have if this ray is to be totally...

Q: The current in an ac power line changes direction 120 times per

The current in an ac power line changes direction 120 times per second, and its average value is zero. Explain how it is possible for power to be transmitted in such a system.

Q: Sunlight or starlight passing through the earth’s atmosphere is always bent toward

Sunlight or starlight passing through the earth’s atmosphere is always bent toward the vertical. Why? Does this mean that a star is not really where it appears to be? Explain.

Q: Is it possible for the power factor of an L-R

Is it possible for the power factor of an L-R-C series ac circuit to be zero? Justify your answer on physical grounds.

Q: If you look up from underneath toward the surface of the water

If you look up from underneath toward the surface of the water in your aquarium, you may see an upside-down reflection of your pet fish in the surface of the water. Explain how this can happen.

Q: In an L-R-C series circuit, what are

In an L-R-C series circuit, what are the phase angle ɸ and power factor cos ɸ when the resistance is much smaller than the from resonance? Explain.

Q: When an L-R-C series circuit is connected across

When an L-R-C series circuit is connected across a 120-V ac line, the voltage rating of the capacitor may be exceeded even if it is rated at 200 or 400 V. How can this be?

Q: A beam of light goes from one material into another. On

A beam of light goes from one material into another. On physical grounds, explain why the wavelength changes but the frequency and period do not.

Q: A student claimed that, because of atmospheric refraction (see Discussion

A student claimed that, because of atmospheric refraction (see Discussion Question Q33.2), the sun can be seen after it has set and that the day is therefore longer than it would be if the earth had n...

Q: As shown in Fig. E33.11, a layer of

As shown in Fig. E33.11, a layer of water covers a slab of material X in a beaker. A ray of light traveling upward follows the path indicated. Using the information on the figure, find a. the index o...