Scientists Say: Hertz | Science News for Students

# Scientists Say: Hertz

This unit of frequency measures how often something repeats each second
Aug 5, 2019 — 6:30 am EST

#### Hertz (noun, “HER-tz”)

This is a unit of frequency. Frequency is the number of times that an event occurs in a given length of time. For example, a hummingbird’s heart can beat (a periodic action) as fast as 1,260 times per minute. That’s a frequency. Scientists can measure that frequency in hertz. One hertz is equal to one cycle per second. If hummingbird’s heart beats at 1,260 beats per minute, that’s 21 beats per second, a frequency of 21 hertz.

Many things can be measured in hertz, from waves beating on a beach to the frequency of sounds. Our range of hearing extends from about 20 hertz (which we hear as a very low pitch) to 20,000 hertz (a very high pitch). So a hummingbird’s heart might sound like a very low hum.

The unit hertz is named for Heinrich Rudolf Hertz, a German physicist who lived from 1857 to 1894. He proved the existence of electromagnetic waves — waves of energy including visible light, radio waves, microwaves and more. All of those waves can now be measured in hertz.

#### In a sentence

Playing sound frequencies around 25,000 hertz might annoy deer enough to keep them away from dangerous roads.

## Power Words

###### (more about Power Words)

electromagnetic     An adjective referring to light radiation, to magnetism or to both.

frequency     The number of times some periodic phenomenon occurs within a specified time interval. (In physics) The number of wavelengths that occurs over a particular interval of time.

hertz     The frequency with which something (such as a wavelength) occurs, measured in the number of times the cycle repeats during each second of time.

microwaves     An electromagnetic wave with a wavelength shorter than that of normal radio waves but longer than those of infrared radiation (heat) and of visible light.

pitch     (in acoustics) The word musicians use for sound frequency. It describes how high or low a sound is, which will be determined by the vibrations that created that sound.

radio     To send and receive radio waves, or the device that receives these transmissions.

radio waves     Waves in a part of the electromagnetic spectrum. They are a type that people now use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals. They also are used in radar.

range     The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists. (in math or for measurements) The extent to which variation in values is possible. Also, the distance within which something can be reached or perceived.

wave     A disturbance or variation that travels through space and matter in a regular, oscillating fashion.