Speed ​​of Light x Speed ​​of Sound

During June festival periods, fireworks are widely used by revelers, who celebrate their devotions with the bangs and luminosity of these “rockets”.

The rocket's explosion produces a light it is a sound. That way, if we're right distance from the party location, we can see the light of the fireworks and then we hear sound of the explosion of these artifacts.

In a storm, before we hear the noise of the Thunder, we see the flash of lightning. Why do we see the light and only then did we hear the sound?

speed of light and speed of sound

This is because the velocity of light is much higher than the speed of sound. THE speed of light is approximately 300,000 km/s, and the speed of sound reaches about 340 m/s (1224 km/h). Thunder noise is a sound wave produced by the movement of electrical discharges in the atmosphere, which can happen in three ways:

• Between cloud and ground;
• Between ground and cloud and
• Among clouds.

A simple calculation to know the approximate location of electrical discharges can be performed as follows:

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Mark the time between the brightness of the lightning it's the sound of Thunder. Let's assume that three seconds elapse between the electrical discharge and the thunder. Multiply the time by velocityofsound: 3 x 340 = 1020. We can see, then, that the interaction of electrical charges occurred at a distance of 1020 meters from the observer.

Application
A group of army soldiers is camped in an ecological reserve. The group's sergeant carried out the following training: using an amateur radio, contacted another team several meters away and ordered a rocket to be launched upwards. The time elapsed between the light it's the sound it was six seconds. The sergeant's team must orient themselves by the rocket and determine the approximate distance of the other group. How are they supposed to do this?

Solution:

Starting from the idea of speed ofsound, they will be able to mark the time between the light of the rocket and the sound, which was six seconds, and multiply that time by the velocityofsound.

6 x 340 = 2040 meters

The other team is therefore at a distance of 2040 meters.

By Luiz Paulo Moreira
Graduated in Mathematics

Would you like to reference this text in a school or academic work? Look:

SILVA, Luiz Paulo Moreira. "Speed ​​of Light vs. Speed ​​of Sound"; Brazil School. Available in: https://brasilescola.uol.com.br/matematica/velocidade-luz-x-velocidade-som.htm. Accessed on June 27, 2021.