Questions from Modern Physics

Q: For a person with normal hearing, the faintest sound that can

For a person with normal hearing, the faintest sound that can be heard at a frequency of 400 Hz has a pressure amplitude of about 6.0 × 10-5 Pa. Calculate the (a). intensity; (b). sound intensity le...

Q: When water is placed in ice-cube trays in a freezer

When water is placed in ice-cube trays in a freezer, why doesn’t the water freeze all at once when the temperature has reached
C? In fact, the water freezes first in a layer adjacent to the sides of...

Q: A sound source and a listener are both at rest on the

A sound source and a listener are both at rest on the earth, but a strong wind is blowing from the source toward the listener. Is there a Doppler effect? Why or why not?

Q: Can you think of circumstances in which a Doppler effect would be

Can you think of circumstances in which a Doppler effect would be observed for surface waves in water? For elastic waves propagating in a body of water deep below the surface? If so, describe the circ...

Q: Stars other than our sun normally appear featureless when viewed through telescopes

Stars other than our sun normally appear featureless when viewed through telescopes. Yet astronomers can readily use the light from these stars to determine that they are rotating and even measure the...

Q: A cold block of metal feels colder than a block of wood

A cold block of metal feels colder than a block of wood at the same temperature. Why? A hot block of metal feels hotter than a block of wood at the same temperature. Again, why? Is there any temperatu...

Q: In case 1, a source of sound approaches a stationary observer

In case 1, a source of sound approaches a stationary observer at speed u. In case 2, the observer moves toward the stationary source at the same speed u. If the source is always producing the same fre...

Q: A person pours a cup of hot coffee, intending to drink

A person pours a cup of hot coffee, intending to drink it five minutes later. To keep the coffee as hot as possible, should she put cream in it now or wait until just before she drinks it? Explain.

Q: If you are riding in a supersonic aircraft, what do you

If you are riding in a supersonic aircraft, what do you hear? Explain. In particular, do you hear a continuous sonic boom? Why or why not?

Q: It is well known that a potato bakes faster if a large

It is well known that a potato bakes faster if a large nail is stuck through it. Why? Does an aluminum nail work better than a steel one? Why or why not? (Note: Don’t try this in a microwave oven!) Th...