Physics

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... »

The Physics Philes, lesson 107: The Subjective Side of Physics

The Physics Philes, lesson 107: The Subjective Side of Physics

We’ve been riding waves for a while now, and last week we dove head-long into sound waves. Sound is particularly interesting, I think, because it’s really easy to illustrate how physics informs how our bodies react to external stimuli. What you hear when you hear a sound is directly related to the sound wave’s physical characteristics. The greater the pressure amplitude (the maxi... »

The Physics Philes, lesson 106: The Sound of Physics

The Physics Philes, lesson 106: The Sound of Physics

We’ve just spent basically forever getting our hands dirty with mechanical waves. Now it’s time to get our hands even dirtier with a specific type of mechanical wave: the sound wave. Sound waves are something most of us are familiar with. The general definition of sound is actually quite simple. Sound is just a longitudinal wave in a medium. Sound waves can travel though anything ̵... »

The Physics Philes, lesson 105: Physics Makes Beautiful Music

The Physics Philes, lesson 105: Physics Makes Beautiful Music

Over these past several weeks, we’ve learned a lot about mechanical waves. However, what we’ve learned is a simple version of the waves we come in contact with every day. For example, the sound string instruments make are complex standing waves. To illustrate this, let’s think about what would happen if a string vibrated at one frequency. If we displace a string so the shape it m... »

The Physics Philes, lesson 104: Standing O for Standing Waves

The Physics Philes, lesson 104: Standing O for Standing Waves

Now that we have nodes, antinodes, and standing waves under our belt, it’s time to move on to something called normal modes. But wait. Let’s step back a bit. As we were learning about standing waves, we didn’t care so much about the length of the string or what was happening on the free end of the string. But now we need to think about a string of a finite length that is held fix... »

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