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Electromagnetic Radiation:
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Learning Targets:
Students will be able to...
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READ: Energy as Waves
We use energy every day to run our appliances, fuel our cars, and cook our food. However, only one form of energy can travel through the vacuum of space: Electromagnetic Radiation. There are many different forms of Electromagnetic Radiation (EMR) but the only form visible to human eyes is light. Visible light can come from many sources and can be different colors but is only a tiny sliver of the total amount of EMR that constantly surrounds us.
The Electromagnetic Spectrum displays the entire range of EMR that exists. From radio waves to gamma rays, most of the EMR in the universe is invisible to us but we use it every day!
We use energy every day to run our appliances, fuel our cars, and cook our food. However, only one form of energy can travel through the vacuum of space: Electromagnetic Radiation. There are many different forms of Electromagnetic Radiation (EMR) but the only form visible to human eyes is light. Visible light can come from many sources and can be different colors but is only a tiny sliver of the total amount of EMR that constantly surrounds us.
The Electromagnetic Spectrum displays the entire range of EMR that exists. From radio waves to gamma rays, most of the EMR in the universe is invisible to us but we use it every day!
WATCH: Wave Properties
Like any other wave, EMR has a frequency, measured in Hertz, which counts the number of waves that pass by a point in one second. Another closely related property is wavelength: the distance from the peak of one wave to the peak of the next. These two measurements are inversely related: the larger the frequency, the smaller the wavelength (and vice versa). Unlike many waves, EMR can also be described by its amount of electron volts, also known as its amount of energy. Therefore, there are three measurements for each type of EMR: frequency, wavelength, and electron volts. These three measurements for describing EM Radiation allow scientists to use whatever range of numbers is more "friendly" for discussion (not too large or too small of a number) and is more relevant to what measurement is being studied. The different types of EMR travel with different wavelengths and frequencies.
Electromagnetic waves differ from sound waves and ocean waves because they do not require a medium (type of matter) through which to travel but instead they require an alternating electric field and magnetic field (hence electromagnetic!).
What all types of EM Radiation have in common:
Electromagnetic waves differ from sound waves and ocean waves because they do not require a medium (type of matter) through which to travel but instead they require an alternating electric field and magnetic field (hence electromagnetic!).
What all types of EM Radiation have in common:
- 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
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: What is 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. Based on the frequency and wavelength, what type of EM Radiation is this?
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: What is 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. Based on the frequency and wavelength, what type of EM Radiation is this?
READ: Types of Electromagnetic Radiation
Radio Waves: Your favorite radio stations use radio waves to send tunes through the atmosphere and to your radio! As shown in the image to the right, AM radio stations use "amplitude modulation" while FM radio stations use "frequency modulation" to send audio information in each wave. AM stations broadcast at a lower frequency (535 - 1700 kilohertz) and signals can travel long distances from the station because the waves get reflected back to Earth by ions in the atmosphere. FM stations broadcast at a higher frequency (88 - 108 megahertz) and signals are lost when traveling more than 40 miles from the station.
Microwaves: Your microwave oven creates microwaves to heat food by energizing water molecules within the food. Microwaves are also used by the weather radar because they can travel through clouds and light rain. Background Microwave Radiation exists in all parts of our Universe and is evidence of the initial energy of the Big Bang and the expansion of the Universe.
Infrared Radiation: Night vision goggles can see the heat emitted by skin because any object that gives off heat also gives off infrared waves. A television remote control uses specific wavelengths of infrared energy to communicate with a receiver.
Visible Light: Our eyes are able to detect visible light as emitted by stars, light bulbs, and even fireflies.
Ultraviolet Light: Sunburns are caused by the damaging UV rays from the sun but luckily our Ozone layer protects us from the majority of UV rays. Some insects can see in the UV spectrum and this causes them to be drawn to specific flowers.
X-Rays: Doctors use x-rays to see through soft tissue to find broken bones while airport security uses x-rays to look for weapons and other items made of metal.
Gamma Rays: Doctors can also use gamma rays to see inside the human body using a positron emission tomography (PET) scan to look for cancer. Gammas are also produced by high energy nuclear explosions and supernovae.
Radio Waves: Your favorite radio stations use radio waves to send tunes through the atmosphere and to your radio! As shown in the image to the right, AM radio stations use "amplitude modulation" while FM radio stations use "frequency modulation" to send audio information in each wave. AM stations broadcast at a lower frequency (535 - 1700 kilohertz) and signals can travel long distances from the station because the waves get reflected back to Earth by ions in the atmosphere. FM stations broadcast at a higher frequency (88 - 108 megahertz) and signals are lost when traveling more than 40 miles from the station.
Microwaves: Your microwave oven creates microwaves to heat food by energizing water molecules within the food. Microwaves are also used by the weather radar because they can travel through clouds and light rain. Background Microwave Radiation exists in all parts of our Universe and is evidence of the initial energy of the Big Bang and the expansion of the Universe.
Infrared Radiation: Night vision goggles can see the heat emitted by skin because any object that gives off heat also gives off infrared waves. A television remote control uses specific wavelengths of infrared energy to communicate with a receiver.
Visible Light: Our eyes are able to detect visible light as emitted by stars, light bulbs, and even fireflies.
Ultraviolet Light: Sunburns are caused by the damaging UV rays from the sun but luckily our Ozone layer protects us from the majority of UV rays. Some insects can see in the UV spectrum and this causes them to be drawn to specific flowers.
X-Rays: Doctors use x-rays to see through soft tissue to find broken bones while airport security uses x-rays to look for weapons and other items made of metal.
Gamma Rays: Doctors can also use gamma rays to see inside the human body using a positron emission tomography (PET) scan to look for cancer. Gammas are also produced by high energy nuclear explosions and supernovae.
WATCH: Electromagnetic Spectrum Videos
Radio Waves
Visible Light Gamma Rays |
Microwaves
Ultraviolet |
Infrared
X-Rays |
ONLINE PRACTICE:
Try these online practice quizzes to gauge your understanding: EM Radiation Quiz Spectrum Quiz
Try these online practice quizzes to gauge your understanding: EM Radiation Quiz Spectrum Quiz
ANSWER: Discussion Questions
Write your responses and submit to Ms. Hinkhouse.
Write your responses and submit to Ms. Hinkhouse.
- Remember, all EM Radiation travels at 3.0 x 10^8 m/s through a vacuum. Calculate the wavelength of radiation with a frequency of 5.10 x 10^14 Hz. In what part of the EM Spectrum does this radiation fall?
- What is the frequency of radiation with a wavelength of 5.00 x 10^-8 m? In what part of the EM Spectrum does this radiation fall? (note: the exponent is negative 8)
- The KMA radio station broadcasts at 960,000 Hz. What is the wavelength of that radiation?
- On faucets, blue means Cold while red means Hot. Explain why this is backwards in terms of light energy.
- Do some research and list the types of EM Radiation produced/used in the following situations:
ASSESS: In Class
On Wednesday, October 1 there will be an in-class quiz related to the Learning Targets listed at the top of this page.
On Wednesday, October 1 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.