Gelombang Bunyi dan Rumus Fisikanya (Belajar Fisika SMP Kelas 8) - Kak Hasan

Summary

In this educational video, the presenter explains the concept of sound waves, covering topics such as the nature of mechanical waves and the requirements for sound to travel. Key concepts include the different types of sound waves based on frequency—infra-sound, audible sound, and ultra-sound. The video also discusses the necessary conditions for hearing sound, such as a source, medium, and the human ear's frequency range. Additionally, the presenter shares a formula for calculating the speed of sound and demonstrates its application with a real-world example. The episode concludes with a preview of upcoming topics on sound reflection and further wave calculations.

Takeaways

• 😀 Sound waves are mechanical waves, which means they require a medium (like air) to travel. Without a medium, such as in space, sound cannot be heard.
• 😀 For sound to be heard, three conditions must be met: a sound source, a medium for transmission, and a listening device (like the human ear).
• 😀 Human hearing is limited to sound frequencies between 20 Hz and 20,000 Hz, known as the audiosonic range.
• 😀 Infrasonic waves are sound waves with frequencies below 20 Hz, which humans cannot hear but animals like crickets can.
• 😀 Ultrasonic waves have frequencies above 20,000 Hz, and although humans can't hear them, animals like bats can detect them.
• 😀 Sound waves travel in the form of compressions and rarefactions, making them longitudinal waves.
• 😀 Sound waves are characterized by their frequency, which determines their pitch, and their amplitude, which affects their loudness.
• 😀 The speed of sound in air is approximately 340 meters per second, and it can vary depending on factors like temperature.
• 😀 A practical example of sound speed was given: a lightning strike and thunder, with a 10-second delay in hearing the sound. Using this delay, the distance to the lightning strike can be calculated.
• 😀 Sound speed calculations use the formula: speed = distance/time. For example, with a delay of 10 seconds, the distance to the lightning was calculated as 3400 meters.
• 😀 The episode concludes with a teaser for the next topic, which will cover the reflection of sound and further calculations related to sound waves.

Q & A

What are sound waves?

Sound waves are mechanical waves that require a medium (such as air, water, or solids) to travel. They consist of compressions and rarefactions that move through the medium.

Why can't sound be heard in space?

In space, there is no medium (like air) to transmit sound waves. Without a medium, sound cannot travel, making it impossible to hear anything in space.

What are the three necessary conditions for sound to be heard?

For sound to be heard, three conditions must be met: a sound source, a medium to carry the sound waves, and a receiver (such as human ears) to detect the sound.

What type of wave is sound?

Sound is a longitudinal wave, meaning that the oscillations of the wave are in the same direction as the wave's travel. It involves compressions and rarefactions in the medium.

What are the three types of sound based on frequency?

The three types of sound based on frequency are: infrasonic (below 20 Hz), audiosonic (20 Hz to 20,000 Hz, which humans can hear), and ultrasonic (above 20,000 Hz).

What is infrasonic sound?

Infrasonic sound refers to sounds with frequencies below 20 Hz, which are not audible to humans but can be heard by certain animals like crickets.

What is the audible frequency range for humans?

Humans can typically hear sound frequencies within the range of 20 Hz to 20,000 Hz, which is known as audiosonic sound.

What is ultrasonic sound?

Ultrasonic sound refers to sound waves with frequencies higher than 20,000 Hz. This range includes sounds that are inaudible to humans but can be detected by animals like bats.

How does the speed of sound relate to time in the example with thunder?

In the example of thunder, the sound of the thunder is heard after a delay due to the distance between the lightning and the listener. The speed of sound can be calculated using the formula: speed = distance / time.

What is the formula for calculating the speed of sound?

The formula to calculate the speed of sound is: speed = distance / time, where the speed is typically around 340 m/s in air.