Calculating Frequency and Wavelength

To keep things simpler, and because the metric system is the universal standard in science, we are going to stick to the metric system here.  However, the same principles apply when we use standard units like feet or miles.

Speed of light=c=300,000,000 meters/second

A television wave has a wavelength of about 1 meter.  What is its frequency? (Highlight to read).

(300,000,000 cycles/second).

An FM radio wave has a wavelength of about 3,000,000 meters.  What is its frequency?

(100 cycles/second). This is why FM dials are around this frequency.  FM means Frequency Modulated.

Ultraviolet Light has a wavelength of about 10^-7 meters (0.0000001 meters).  What is its frequency?

3*10^15 cycles/second.  (3,000,000,000,000,000 or 3 quadrillion cycles/second).

A gamma ray has a wavelength of about 10^-12 meters.  What is its frequency?

3*10^20 cycles/second (300,000,000,000,000,000,000 or 300 quintillion cycles per second).

Now we'll give you the frequencies and have you compute the wavelengths:

Infrared Light completes about 10^13 (10,000,000,000,000 or 10 trillion) cycles per second.  What is its wavelength?  3*10^-5 meters or 0.00003 meters

An X-ray completes about 10^18 cycles/second (1,000,000,000,000,000,000 or 1 quintillion).  What is its wavelength?  (3*10^-10 meters or 0.0000000003 meters).

Finally, a microwave completes about 10^9 cycles/second (1,000,000,000 or 1 billion).  What is its wavelength? 0.3 meters.   This is why microwave ovens are about the size they are--and why food needs to be turned to be cooked thoroughly.

The Electromagnetic Spectrum

Visible light actually composes a very small part of The Electromagnetic Spectrum.

As seen above (click on image to view larger version), the electromagnetic spectrum also consists of Radio Waves, TV waves, Microwaves, Infrared Waves, Ultraviolet Waves, X-rays, and Gamma Rays, in addition to visible light.

Remember yesterday's activity (Learning Activity/Authentic Assessment #2)?  We found that when we take many small steps to match the same speed as someone taking fewer large steps.

Each part of the electromagnetic spectrum travels at the same speed, the speed of light (186,282 miles/second or 300,000,000 meters/second).  Those parts of the electromagnetic spectrum which have a shorter wavelength must then complete more cycles/second.  Those parts which have longer wavelengths must complete fewer cycles/second.  It's just like the pace length and number of steps.

Visible white light is composed of all colors of the visible spectrum

The colors are arranged according to their wavelengths.  Violet has a wavelength of about 400 nm (4 * 10^-7 meters or 0.0000004 meters), while red has a wavelength of about 700 nm (7*10^-7 meters or 0.0000007 meters).

But clearly, these aren't all the numbers available.  What if the wavelength were smaller, like say 10^-23 meters (0.00000000000000000000001) meters?  What about larger wavelengths, like a million meters (1,000,000 meters)?

These also exist.