Making Waves with Sound and Light

Summary

This video explores the differences between light and sound waves, highlighting their distinct behaviors. Light, an electromagnetic wave, doesn't need a medium to travel, unlike sound, a mechanical wave requiring solids, liquids, or gases. Demonstrations using a vacuum chamber show light can travel through a vacuum but sound cannot. The video also explains the delay between seeing lightning and hearing thunder due to the vastly different speeds of light and sound, allowing viewers to estimate distances to storms using the delay.

Takeaways

• 🌌 Light and sound are both waves, but they behave differently as light is an electromagnetic wave and sound is a mechanical wave.
• 🌐 Sound requires a medium like solid, liquid, or gas to travel, whereas light does not need a medium for propagation.
• 📱 A demonstration with a cell phone in a vacuum chamber shows that light can be seen without a medium, but sound cannot be heard.
• ⏱️ There's a significant delay between seeing and hearing due to the different speeds of light and sound, with light being much faster.
• ⚡️ The delay between seeing lightning and hearing thunder is a practical example of the difference in speed between light and sound.
• 📏 The speed of light is approximately 186,000 miles per second, while the speed of sound is about 0.2 miles per second.
• 🔍 By observing the delay between an event's light and sound, one can estimate distances, such as the distance to a storm.
• 📐 A general rule of thumb is that a 5-second delay in hearing thunder after seeing lightning corresponds to about 1 mile distance.
• 🎥 The video example illustrates how to calculate the distance to an event by using the delay between seeing an explosion and hearing the sound.
• 🧮 The calculation method involves multiplying the delay in seconds by the speed of sound to find the distance in miles.

Q & A

What are the two types of waves discussed in the script?

The script discusses two types of waves: light, which is an electromagnetic wave, and sound, which is a mechanical wave.

Why does sound require a medium to propagate?

Sound is a mechanical wave and needs a medium like a solid, liquid, or gas to travel through because it involves the vibration of particles in that medium.

How does the propagation of light differ from sound?

Light is an electromagnetic wave and does not require a medium to propagate; it can travel through a vacuum.

What happens to sound when air is removed from a vacuum chamber?

When air is removed from a vacuum chamber, sound cannot travel because there is no medium for the sound waves to propagate through.

Why can we still see light when the phone is in a vacuum chamber?

We can see light from the phone screen in a vacuum chamber because light is an electromagnetic wave and does not require a medium to travel; it can propagate through a vacuum.

What is the speed of light in miles per second?

The speed of light is approximately 186,000 miles per second.

What is the speed of sound in miles per second?

The speed of sound is about 0.2 miles per second.

Why do we see lightning before we hear thunder?

We see lightning before we hear thunder because light travels much faster than sound, causing a delay between the visual and auditory perception of a storm.

How can the delay between seeing lightning and hearing thunder be used to estimate the distance to a storm?

The delay between seeing lightning and hearing thunder can be used to estimate the distance to a storm by multiplying the delay in seconds by the speed of sound (0.2 miles per second).

What is the general rule for estimating the distance to a storm based on the delay between lightning and thunder?

As a general rule, every 5 seconds delay in hearing thunder after seeing lightning corresponds to approximately 1 mile distance from the storm.

How can the viewer estimate the distance to an explosion using the information provided in the script?

The viewer can estimate the distance to an explosion by multiplying the delay in seconds between seeing the light and hearing the sound by the speed of sound (0.2 miles per second).

Outlines

00:00

🌌 Understanding Light and Sound Waves

This paragraph introduces the fundamental differences between light and sound waves. Light is an electromagnetic wave that can travel through a vacuum, whereas sound is a mechanical wave requiring a medium like solids, liquids, or gases to propagate. The speaker, Dan, an MIT undergraduate, uses a vacuum chamber to demonstrate how sound cannot travel in a vacuum, unlike light. This experiment visually and audibly illustrates the dependency of sound on a medium, while light continues to be visible even in the absence of air or other gases.

Keywords

💡Light

Light is an electromagnetic wave that can travel through a vacuum without the need for a medium. In the video, light's ability to propagate in a vacuum is demonstrated by observing a phone's screen light in a vacuum chamber. This experiment illustrates that light can be seen even in the absence of air or other gases, highlighting its fundamental difference from sound waves.

💡Sound

Sound is a mechanical wave that requires a medium, such as air, water, or solids, to travel through. The video explains that sound cannot propagate in a vacuum, as shown when the phone's ringtone is inaudible once the vacuum chamber is evacuated. This property is contrasted with light to emphasize the distinct behaviors of these two types of waves.

💡Mechanical Wave

A mechanical wave, like sound, is a disturbance that travels through a medium by the movement of particles in that medium. The video uses the example of sound to explain mechanical waves, noting that they cannot exist in a vacuum, which is a key point in understanding why the ringtone is silent when the air is removed.

💡Electromagnetic Wave

Electromagnetic waves, like light, are waves that consist of oscillating electric and magnetic fields and can travel through a vacuum. The video highlights that light is an electromagnetic wave, which is why it can be observed on the phone screen even when the chamber is devoid of matter.

💡Propagation

Propagation refers to the process by which waves spread out from their source. The video discusses how sound and light propagate differently, with sound needing a medium and light not requiring one, as demonstrated by the vacuum chamber experiment.

💡Vacuum Chamber

A vacuum chamber is a space from which air and other gases have been removed to create a low-pressure environment. In the video, a vacuum chamber is used to demonstrate the difference in propagation between sound and light, showing that light can be seen but sound cannot be heard when the chamber is evacuated.

💡Speed of Light

The speed of light is approximately 186,000 miles per second in a vacuum. The video mentions this speed to explain the near-instantaneous nature of light's propagation, which is much faster than sound and results in a delay between seeing lightning and hearing thunder.

💡Speed of Sound

The speed of sound is about 0.2 miles per second in air at sea level. The video uses this speed to calculate the distance to a storm by timing the delay between seeing lightning and hearing thunder, illustrating how the speed of sound can be used to estimate distances.

💡Delay

Delay in the context of the video refers to the time lag between the occurrence of two events, such as seeing lightning and hearing thunder. The video explains that because light travels much faster than sound, there is a noticeable delay, which can be used to estimate distances, as shown in the example of the lightning and thunder.

💡Distance Estimation

Distance estimation is the process of determining how far away an event is based on observable phenomena. The video provides a method for estimating the distance to a storm by counting the delay between lightning and thunder and multiplying it by the speed of sound, as demonstrated with the example of the 17-second delay.

💡Man Vehicle Lab

The Man Vehicle Lab at MIT is mentioned as the affiliation of the speaker, Dan. It's a research lab that focuses on human-machine interactions, which provides context to the speaker's expertise and the setting in which the video's experiments and explanations are conducted.

Highlights

Light and sound are both waves that travel through time and space, but they have different behaviors and properties.

Sound is a mechanical wave that requires a medium like solid, liquid, or gas to propagate.

Light is an electromagnetic wave that does not require a medium for propagation.

A vacuum chamber experiment demonstrates that sound cannot travel in a vacuum, unlike light.

The speed of light is 186,000 miles per second, much faster than the speed of sound at 0.2 miles per second.

The delay between seeing lightning and hearing thunder is due to the difference in the speed of light and sound.

The further you are from a storm, the larger the delay between seeing lightning and hearing thunder.

The speed of light is so high that its transmission can be considered instantaneous.

Using the delay between the explosion of light and noise, one can estimate the distance to the event.

A general rule is that every 5 seconds delay corresponds to a distance of 1 mile.

The video demonstrates how to calculate the distance to a lightning strike using the delay between lightning and thunder.

The viewer was 0.6 miles from the lightning strike based on the 3-second delay.

A practical example is given to calculate the distance to a storm by counting the delay between lightning and thunder.

The experiment with the phone in a vacuum chamber shows that light can be seen but not the sound when air is removed.

The experiment illustrates the fundamental difference between how light and sound waves behave in the absence of a medium.

The video provides a clear demonstration of the practical applications of understanding the speed of light and sound.

A step-by-step guide is given on how to estimate the distance to a storm using the 5-second rule for sound delay.

Transcripts

we talk we listen we see we use sound

and light every day

all the time but do we really know their

behavior what causes it the delay

between seeing and hearing the firework

hi I'm Dan an MIT undergraduate from the

man vehicle lab and I'm here to talk to

you about the differences between light

and sound light and sound are both waves

that travel through time and space

accompanied by the transference of

energy from one point to another but

this is where the similarities end

sound is a mechanical wave that requires

a medium to propagate through such as a

solid liquid or gas whereas light is an

electromagnetic wave that doesn't

require a propagation medium let's go

see the effects of these different

behaviors you probably use your phone

every day and as you can see when

someone's calling me I can see the light

on the screen and the sound of the

ringtone

now we're going to use the vacuum

chamber we're going to put the cell

phone inside the vacuum chamber and then

turn it on when I turn it on a vacuum

pump will remove the air or other gases

from inside the chamber leaving a

low-pressure environment this

environment will be completely void of

matter just like space look I'm

receiving a phone call again and I can

see the light but what about the sound

of the ringtone and now with no vacuum

we can hear the ringtone again Oh gross

it's my mom we've got to put that back

in the vacuum chamber surely you're

familiar with storms and how we see the

Lightning first and then we hear the

Thunder this is because the speed of

light is 186,000 282 miles per second

whereas the speed of sound is only 0.2

miles per second because of this huge

difference there's a delay between

seeing the light and hearing the sound

and the further you are from the storm

the larger this delay is but this

doesn't only apply to other storms it

also applies to other everyday

situations remember that video from

earlier let's go look at it again as you

noticed we can see the explosion of

light in the sky and just some seconds

later you can hear the sound the delay

was about three seconds and with

information we can estimate the distance

between the viewer and the burst the

speed of light is so high with

transmission of light and be considered

instantaneous so multiplying the speed

of sound by the delay between the

explosion of light and noise we get the

distance in this case the viewer was 0.6

miles from the murder ship and as a

general rule we can assume that every 5

seconds delay corresponds to a distance

of 1 mile now you can know how far away

storm is by doing a few simple

calculations now try it on your own with

the following storm video determine the

distance using the delay between the

lightning and thunder

you

you should have counted about 17 seconds

multiplying this by the speed of sound

of 0.2 miles per second you should get a

distance of 3.4 miles

you