![]() What three examples of electromagnetic energy are mentioned in the text? Q43. Table 1-2.≼omparison of Light Waves and Sound Waves SOUND WAVES LIGHT WAVES VELOCITY IN AIR APPROXIMATELY 1,100 FEET PER SECOND APPROXIMATELY 186,000 MILES PER SECOND FORM A FORM OF WAVE MOTION A FORM OF WAVE MOTION WAVE COMPOSITION LONGITUDINAL TRANSVERSE TRANSMITTING MEDIUM ALL SUBSTANCES EMPTY SPACE AND ALL SUBSTANCES EXCEPT OPAQUE MATERIALS RELATION OF TRANSMITTING MEDIUM VELOCITY TO VELOCITY THE DENSER THE MEDIUM, THE GREATER THE SPEED THE DENSER THE MEDIUM, THE SLOWER THE SPEED SENSATIONS PRODUCED HEARING SEEING VARIATIONS IN SENSATIONS PRODUCED A LOW FREQUENCY CAUSES A LOW NOTE A HIGH FREQUENCY, A HIGH NOTE A LOW FREQUENCY CAUSES RED LIGHT A HIGH FREQUENCY, VIOLET LIGHT Q42. For example, I know that the speed of sound is 343 in room at 20 0 C. For a comparison of light waves with sound waves, see table 1-2. okay, so I know that light is faster than sound, and we can prove it with many visuals, but can y'all give examples of speeds through the same medium. A change in the frequency of a light wave causes a visual sensationa difference in color. A change in frequency of sound waves causes an audible sensationa difference in pitch. Violet light is produced at the high- frequency end of the light spectrum, while red light is produced at the low-frequency end of the light spectrum. Likewise, a certain range of light frequencies produces sensations that you can see. A more rapid sound vibration (higher frequency) produces a higher note. A slow vibration ( low frequency) in sound gives the sensation of a low note. A certain range of sound frequencies produces sensations that you can hear. Sound travels through all substances, but light cannot pass through opaque materials. ![]() ![]() Light travels approximately one-third slower in water than in air. The denser the medium, the greater the speed of sound. Although both are forms of wave motion, sound requires a solid, liquid, or gaseous medium whereas light travels through empty space. The second difference is that sound is composed of longitudinal waves (alternate compressions and expansions of matter) and light is composed of transverse waves in an electromagnetic field. Sound waves travel through air at the speed of approximately 1,100 feet per second light waves travel through air and empty space at a speed of approximately 186,000 miles per second. It may seem to flicker.1-32 COMPARISON OF LIGHT WAVES WITH SOUND WAVES There are two main differences between sound waves and light waves. Thats not the whole story, however - a lightning flash may have only one return stroke or may have several tens of strokes using the same column of ionized air. A powerful "return stroke" releases much more energy. Most of the charge flows after this leader makes electrical contact with the ground, however. The whole process may take a few milliseconds (one-thousanths of a second), providing enough time to perceive motion. There is a pause between steps of about 50 microseconds. The "leader", the first stroke of a lightning discharge, actually proceeds in steps - lengthening by about 30 meters at a time, taking about a microsecond (one millionth of a second) to do each step. They crash into air molecules on their way down and free other electrons, making a tube of ionized air. They are accelerated by a strong electric field, a consequence of the big voltage difference between the cloud and the ground. A lightning discharge consists of electrons which have been stripped from their molecules flying through the air. ![]() The bottom tip of a lightning bolt traveling from a cloud to the ground does travel rather quickly, although it travels at much less than the speed of light.
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