Physics

The Physics Philes, lesson 115: The Doppler Shift

The Physics Philes, lesson 115: The Doppler Shift

We’ve been talking, over the last several weeks, about sound and sound waves and how those waves interact with each other. Implicit in those discussions is the assumption that everyone is at rest relative to one another. That’s not always how it works. We know, of course, that we can hear things eve if they are moving. It would be a pretty weird world if we couldn’t. But that doe... »

The Physics Philes, lesson 114: We Got da Beats

The Physics Philes, lesson 114: We Got da Beats

Remember last week we learned all about wave interference. As I mentioned at the end of that post, we stuck to waves that have the same frequency. But that’s not always how things work out in the real world. Something slightly different happens when we have two waves overlap that have slightly different frequencies, and all we have to do is apply some concepts we already know and love. Let&#... »

The Physics Philes, lesson 113: Don’t Interfere (Or Do)

The Physics Philes, lesson 113: Don’t Interfere (Or Do)

So far in our discussion of waves we’ve basically been working with one wave at a time. But that’s not really how waves work in real life. Waves from different sources are constantly bouncing around. Modern life is a cacophony. Physics can tell us how those waves interact. With all the waves flying around, some of those waves are going to overlap. This is called interference, and we... »

The Physics Philes, lesson 112: Sea Shell Resonance

The Physics Philes, lesson 112: Sea Shell Resonance

I know last week I said that we’d look at how standing sound waves applied to musical instruments, but as I was preparing I realized that it doesn’t really illuminate anything, so I’m moving on resonance and sound. Sound good to you? Great. Remember that a normal mode is when all the particles in the oscillating system move sinusoidally with the same frequency. If we can get the ... »

The Physics Philes, lesson 111: The Legend of Kundt’s Tube

The Physics Philes, lesson 111: The Legend of Kundt’s Tube

So far in our discussion of waves, we’ve learned about nodes, antinodes, and standing waves. However, we’ve really only seen what these looks like with respect to transverse waves on a string. But sound waves are longitudinal waves. How do these concepts apply? As it turns out, much the same way as with transverse waves. Rather than a string, let’s think about a longitudinal wave... »

The Physics Philes, lesson 110: Ring My Decibel

The Physics Philes, lesson 110: Ring My Decibel

OK, friends. Let’s talk about wave intensity. Wave intensity (denoted with an I) is the average rate of time energy is transported per unit area across a surface that is perpendicular to the direction of propagation. So, if we’re talking about a transverse wave on a string, the wave might be propagating right to left. That means that the relevant surface for calculating wave propagatio... »

The Physics Philes, lesson 109: Speed of Sound Part 2

The Physics Philes, lesson 109: Speed of Sound Part 2

Last week we started discussing the speed of sound and how that speed changes depending on the medium. This week we’ll finish up that topic with a discussion of how fast sound moves in a solid and a gas. First, let’s tackle the speed of sound through a solid rod or bar. Unlike fluid in a pipe (which cannot move sideways), the solid rod can expand slightly when it’s compressed by ... »

The Physics Philes, lesson 108: The Speed of Sound

The Physics Philes, lesson 108: The Speed of Sound

Last week we talked a bit about how our ears work and how they perceive sound. If we’re having a conversation, the sound seems to travel from my mouth to your ears in an instant. But what do you hear in a thunder storm? We know that thunder is the sound we hear as the air around a lightning bolt rapidly expands. We also probably know from experience that we see the lightning bolt before we h... »

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