LIGHT Overview An electromagnetic wave is made up of vibrating electrical and magnetic fields that travel as quickly as light. Unlike many other types of waves, electromagnetic waves do no require a medium to pass through. Models of Light Wave Action The diagram above is one of two models of electromagnetic waves. This one is called the wave model. Notice in this model how the two fields are vibrating at 90 degree angles to each other. This model does simplify normal wave action. In fact, when electromagnetic waves travel, the waves travel in many different directions. Another model of wave action is the particle model. This model suggests that electromagnetic waves sometimes cause electrons to move around and create an electric field. In this model light travels a stream of small particles of energy called photons. LESSON CHECKPOINT: Explain the two models for electromagnetic waves. Wave Speed The speed of an electromagnetic wave is calculated by multiplying the wavelength by the frequency. In a vacuum, all electromagnetic waves travel at the same speed even though they have different wavelengths. The variations in wavelength are compensated by variations in frequency leaving the speed the same. The diagram below shows the electromagnetic spectrum or complete range of all electromagnetic wavelengths. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
The diagram above shows the various types of electromagnetic radiation and the differences in their wavelengths and frequencies. Notice that the radio waves on the left have larger wavelengths and lower frequencies while the gamma rays on the far right, have shorter wavelengths and greater frequencies. LESSON CHECKPOINT: What types of waves are in the electromagnetic spectrum? Visible Light Visible light makes up just a small part of the electromagnetic spectrum but it too can be broken up into different wavelengths. When passed through a glass prism, an ordinary light beam refracts into the many different colors or wavelengths of light. The diagram below shows this refraction of light. LESSON CHECKPOINT: How do these differences in wavelengths result in seeing different colors? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
When light hits an object, it either goes through easily, partially, or not at all. An object that lets most of the light through is said to be transparent. An example would be a window. Objects that allow only some light to get through are called translucent. An example of this is frosted glass. An opaque object prevents all light from getting through it and an example would be a solid brick wall. LESSON CHECKPOINT: What is the difference between transparent, translucent, and opaque objects? Colors The colors we see depend upon which wavelengths of visible light get reflected back to our eyes. For example, when ordinary light is shone on a green object, the green pigment of the object absorbs all the wavelengths except green and reflects only this wavelength back to our eyes. Objects appear white when they reflect all of light’s wavelengths and conversely, they look black when they reflect little or none of the wavelengths. This is why it is wise to wear light-colored clothing in the summer; your clothing doesn’t absorb the light and contribute to a feeling of warmth. LESSON CHECKPOINT: Explain how the makeup of light causes us to see different colors. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.