Conceptual Physics POGIL: The Electromagnetic Spectrum



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The Electromagnetic Spectrum POGIL Activity

Wavelength (() - Units: m, cm, nm

Frequency (() - the # of waves that pass a given point in one second.

Units: Hz, sec-1, waves/sec, 1/sec

The relationship between frequency (f) and wavelength (() of a wave is described by the equation Waves speed = frequency X wavelength OR c = ((

All electromagnetic radiation propagates at a speed of c = 3.00x108 m/sec (approximately 186,000 miles per second) this is called the speed of light!

When solving problems using c (the speed of light) ( MUST be in Hz or sec-1 and ( MUST be in meters.

Problems

1. What is the wavelength of radiation with a frequency of 6.24 x l013 sec-1?

2. What is the frequency of radiation with a wavelength of 2.20 x l0-6 nm? (1 nm = 10-9m or 109nm=1m)

3. A television relay transmitter operates at a frequency of 927.9 MHz. Calculate the wavelength of the signal in nanometers. Is this visible light? (1 MHz = 1,000,000 Hz)

How on earth would I know if it is visible light? Read on to find out!!

The Nature of Electromagnetic Radiation

Electromagnetic radiation includes radio signals, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. One model of electromagnetic radiation is a propagating wave that is partially electric in nature and partially magnetic in nature. The following diagram is a pictorial description of this model:

This type of wave is called an electromagnetic wave.

The Electromagnetic Spectrum

The electromagnetic spectrum is an ordered list of all the types of electromagnetic radiation. All electromagnetic radiation can be described using the wave model or particle model above. The only difference between each type is the wavelength and frequency of the associated electromagnetic wave. The types of radiation and their wavelength ranges are shown in the diagram below.

|Electromagnetic Spectrum | |

|Wavelength |Type of Electromagnetic Radiation |

|5.55 m to 187 m OR (5.55X109 nm to 1.87X1011 nm) |AM Radio |

|0.187 m to 5.55 m OR (1.87X108 nm to 5.55X109 nm) |TV & FM Radio Waves |

|10 mm to 187 mm OR (1X107 nm to 1.87X108 nm) |Microwave |

|750 nm to 1,000,000 nm |Infrared (IR) |

|400 nm to 700 nm |Visible spectrum |

|10 nm to 400 nm |Ultraviolet (UV) |

|Less than 10 nm |X rays |

|Less than 0.001 nm |Gamma (γ) rays |

Problems (Use the diagrams on the previous page to answer these questions.)

4. What is the difference between an X-ray, light, and a radio wave?

5. Which type of electromagnetic radiation has:

a) the longest wavelength?

b) the shortest wavelength?

c) the highest frequency?

d) the lowest frequency?

6. What is the approximate range of wavelengths of visible light? Now go back and answer questions #3!

7. What is meant by the statement “Light is the only thing we can see.”?

Electromagnetic Radiation and Energy

Electromagnetic radiation carries energy with it over space. The energy of a photon (a particle of electromagnetic radiation carrying a quantum of energy) is given by the equation Energy = h X frequency OR E = h(

The constant h is called Planck's constant, equal to 6.63x10─34 J●sec, a very small number.

Frequency (() – must be in Hz or sec-1

Another equation for the energy of a photon is

Energy = h X speed of light OR E = hc

Wavelength (

Problems

8. If a certain light has 7.18 x l0-19 J of energy what is the frequency, in Hz, of this light?

b. What is the wavelength, in nm, of this light?

9. If the frequency of a certain light is 3.8 x l014 Hz, what is the energy of this light?

10. The energy of a certain light is 3.9 x l0-19 J. What is the wavelength, in nm, of this light? Is it visible?

11. List the types of electromagnetic radiation in order from lowest energy photons to highest energy photons.

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electric part of wave

magnetic part of wave

direction of propagation

Higher Frequency

Lower Frequency

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