Amplitude, period, frequency and wavelength of periodic waves | Physics | Khan Academy

Summary

This video explores the fundamental concepts of waves, focusing on how disturbances in a medium, like a string, create pulse and periodic waves. Key properties discussed include amplitude, period, frequency, and wavelength. The relationship between these properties is highlighted through formulas that connect velocity, frequency, and wavelength, allowing viewers to solve wave-related problems. An example illustrates the practical application of these concepts, emphasizing the intuitive understanding of wave mechanics. Overall, the video provides a comprehensive introduction to wave behavior in physics.

Takeaways

• 😀 A disturbance in a string creates a wave, which can propagate through a medium or even in a vacuum.
• 📏 The amplitude of a wave measures how far it moves from its resting position, indicating wave height.
• 🔄 A periodic wave is characterized by repeating cycles, where each cycle includes a full motion up and down.
• ⏳ The period of a wave is the time it takes to complete one full cycle, while frequency measures how many cycles occur per second.
• ⚡ Frequency is the inverse of the period; if the period is 5 seconds, the frequency is 1/5 cycles per second.
• 📏 Wavelength is defined as the distance traveled by the wave during one complete cycle, or the distance between two consecutive peaks or troughs.
• 🚀 The velocity of a wave is determined by the wavelength divided by the period, or equivalently, the product of wavelength and frequency.
• 🧮 The formulas for waves—velocity = wavelength × frequency—allow calculations of wave properties when given two variables.
• 🌊 If the velocity of a wave is known, along with its frequency, the wavelength can be easily calculated.
• 🔍 Understanding these fundamental concepts helps solve various wave-related problems in physics.

Q & A

What is a wave as described in the video?

A wave is a disturbance that propagates through a medium, represented in the video by a string being jerked up and down.

What distinguishes a pulse wave from a periodic wave?

A pulse wave consists of a single disturbance, while a periodic wave is formed by repeated disturbances at regular intervals.

What is amplitude, and how is it measured?

Amplitude is the maximum distance the wave moves from its resting position, measured from the resting position to the peak.

How is wave height different from amplitude?

Wave height is the distance from the trough to the peak of a wave, while amplitude measures from the resting position to the peak.

What does the term 'period' refer to in wave motion?

Period is the time it takes to complete one full cycle of the wave, including going up and down and returning to the starting position.

What is frequency and how is it related to period?

Frequency is the number of cycles that occur per second, and it is the inverse of the period; if the period is long, the frequency is low, and vice versa.

What is the formula that relates velocity, wavelength, and frequency?

The formula is velocity = wavelength × frequency, linking the speed of the wave to its wavelength and how often it oscillates.

How do you calculate wavelength from given velocity and frequency?

You can calculate wavelength by rearranging the velocity formula: wavelength = velocity / frequency.

What unit is used to measure frequency?

Frequency is measured in hertz (Hz), which represents cycles per second.

How can you determine the period if given the frequency?

The period can be calculated as the inverse of frequency: period = 1 / frequency.