Frequency Calculator

What is Frequency?

In physics, frequency describes how often a repeating event occurs per unit of time. Imagine watching waves crash onto a beach. If a new wave hits the shore every second, the frequency is high. If a wave hits every minute, the frequency is low.

The standard unit for measuring frequency is the Hertz (Hz). One Hertz equals "one cycle per second."

• 1 Hz: An event happens once every second.
• 60 Hz: The screen on your computer monitor likely refreshes 60 times per second.
• 440 Hz: The musical note "A" (above middle C). The string vibrates 440 times per second.
• 2.4 GHz: Your Wi-Fi router transmits 2.4 billion signal cycles per second.

Formula 1: Frequency vs. Period

Frequency is intimately tied to Time. Specifically, it is the reciprocal of the Period ($T$). The "Period" is simply the time it takes to complete one full cycle.

Formula 2: Wave Speed & Wavelength

When dealing with waves moving through space (like sound or light), frequency connects velocity and distance. A wave has a certain speed ($v$) and a certain physical length ($\lambda$ - lambda).

Imagine a train (the wave) moving at a constant speed. If the train cars (wavelengths) are very short, more of them will pass you in one second (high frequency). If the cars are very long, fewer will pass you (low frequency).

Frequency of Sound

Sound is a pressure wave moving through air. The speed of sound at sea level is approximately 343 meters per second.

Frequency determines the Pitch of the sound.

• 20 Hz: The lowest rumble a human ear can hear (deep bass).
• 20,000 Hz (20 kHz): The highest screech a human can hear (often lost as we age).

Bats communicate using "Ultrasound"—frequencies above 20 kHz that humans cannot detect. Elephants use "Infrasound"—frequencies below 20 Hz that can travel for miles through the ground.

Frequency of Light (Color)

Light is also a wave, but it travels much faster—approximately 300,000,000 meters per second ($c$).

Just as frequency determines the pitch of sound, frequency determines the Color of light. Your eyes are frequency detectors!

Note: 1 THz (Terahertz) = 1,000,000,000,000 Hz. Visible light waves vibrate trillions of times per second!

Real World Application: Radio & Wi-Fi

Your car radio and home Wi-Fi work on the same principle, just at different frequencies on the Electromagnetic Spectrum.

• FM Radio (100 MHz): These waves are about 3 meters long. They can wrap around buildings and hills easily.
• Wi-Fi (2.4 GHz): These waves are about 12 centimeters long. They are faster (carry more data) but struggle to pass through thick concrete walls compared to radio waves.
• 5G (High Band): Uses extremely high frequencies (millimeter waves). They carry massive data speeds but can be blocked by a simple tree or rain because the wavelength is so short.