Wave Properties
Like any other wave, Electromagnetic Radiation has properties that can be measured and calculated. Wavelength: the distance from the peak of one wave to the peak of the next (measured in meters) Frequency: counts the number of waves that pass by a point in one second (measured in Hertz) These two measurements are inversely related: the larger the frequency, the smaller the wavelength (and vice versa). The different types of EMR travel with different wavelengths and frequencies. |
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What all types of EM Radiation have in common:
- They do not require a medium (type of matter) to travel but instead they require an alternating electric field and magnetic field (hence electromagnetic!).
- The energy travels in "packets" called photons but different types of radiation have different amounts of energy stored in the photons.
- The energy also travels as waves with specific frequencies (measured in Hertz) and wavelengths (measured in meters).
- The energy travels at "the speed of light" through the vacuum of space (3.0 × 10^8 m/s)
- The relationship between speed, wavelength, and frequency is Speed = Wavelength × Frequency
- To solve for wavelength in meters: Wavelength = 3.0 x 10^8 divided by Hertz Frequency
- To solve for frequency in Hertz: Frequency = 3.0 x 10^8 divided by Meters Wavelength
PRACTICE: Wave Properties
Use the information shown above and/or online research to answer the following questions. The answers are given at the bottom of this page.
1. Waves with high frequencies also have higher energy and can damage living cells. Knowing that, which is more dangerous: standing in front of your microwave or getting an X-ray? Why?
2. In the study of sound waves and music, frequency is also known as pitch. Which instrument produces waves with a longer wavelength: a flute or a tuba? Why?
3. Calculate the frequency of a wave if 400,000 wavelengths pass a point every 5 seconds. Use the proper label!
4. Remember, all EM Radiation travels at 3.0 × 10^8 m/s through a vacuum. Use the speed equation shown above to calculate the wavelength of radiation with a frequency of 2.09 × 10^11 Hz.
Use the information shown above and/or online research to answer the following questions. The answers are given at the bottom of this page.
1. Waves with high frequencies also have higher energy and can damage living cells. Knowing that, which is more dangerous: standing in front of your microwave or getting an X-ray? Why?
2. In the study of sound waves and music, frequency is also known as pitch. Which instrument produces waves with a longer wavelength: a flute or a tuba? Why?
3. Calculate the frequency of a wave if 400,000 wavelengths pass a point every 5 seconds. Use the proper label!
4. Remember, all EM Radiation travels at 3.0 × 10^8 m/s through a vacuum. Use the speed equation shown above to calculate the wavelength of radiation with a frequency of 2.09 × 10^11 Hz.
ONLINE PRACTICE:
Try this online practice quiz to gauge your understanding: Calculating Wavelength & Frequency
Try this online practice quiz to gauge your understanding: Calculating Wavelength & Frequency
Discussion Questions
Submit your answers via email. 1. An electromagnetic wave has a frequency of 5.10 x 10^14 Hz. a. Calculate its wavelength in meters. b. In what part of the EM Spectrum does this radiation fall? 2. An electromagnetic wave has a wavelength of 5.00 x 10^-8 m. a. Calculate its frequency in Hertz. (notice the exponent is negative 8) b. In what part of the EM Spectrum does this radiation fall? 3. The KMA radio station broadcasts at 960,000 Hz. What is the wavelength of that radiation? |
ASSESS: In Class
There will be an in-class quiz related to the Learning Targets listed at the top of this page.
There will be an in-class quiz related to the Learning Targets listed at the top of this page.
Answers to Practice:
1. Getting an X-ray is more dangerous for people than standing in front of a microwave because X-rays have a higher frequency and shorter wavelength. As high energy radiation, X-rays have the potential to alter atoms into ions and disrupt the DNA of living things.
2. A tuba makes a sound with a longer wavelength than a flute because a long wavelength relates to a lower frequency and pitch. This also makes sense because a tuba is larger and actually has more space to create a longer wavelength than a small flute.
3. Frequency = cycles ÷ second = 400,000 ÷ 5 = 80,000 Hertz (or 8.0 × 10^4 Hz)
4. Speed = frequency × wavelength
3.0 × 10^8 = frequency × wavelength
3.0 × 10^8 = 2.09 × 10^11 × wavelength
3.0 × 10^8 ÷ 2.09 × 10^11 = wavelength
1.4 × 10^-3 meters = wavelength
This is microwave radiation.
1. Getting an X-ray is more dangerous for people than standing in front of a microwave because X-rays have a higher frequency and shorter wavelength. As high energy radiation, X-rays have the potential to alter atoms into ions and disrupt the DNA of living things.
2. A tuba makes a sound with a longer wavelength than a flute because a long wavelength relates to a lower frequency and pitch. This also makes sense because a tuba is larger and actually has more space to create a longer wavelength than a small flute.
3. Frequency = cycles ÷ second = 400,000 ÷ 5 = 80,000 Hertz (or 8.0 × 10^4 Hz)
4. Speed = frequency × wavelength
3.0 × 10^8 = frequency × wavelength
3.0 × 10^8 = 2.09 × 10^11 × wavelength
3.0 × 10^8 ÷ 2.09 × 10^11 = wavelength
1.4 × 10^-3 meters = wavelength
This is microwave radiation.