Light and Sound
Light and sound is found everywhere. Light and sound waves travel from place to place and can be seen and heard. Light is visible to the human eye and is responsible for the sense of sight. It is a form of energy we can see when it is reflected off the surface of an object. Sound is a mechanical vibration that can pass through solids, liquids, and gases and can usually be identified by the sense of hearing.
Light waves travel through the air from place to place and do not carry matter. Light is believed to travel faster than anything in the universe. It travels at a speed of 186,000 miles per second. Light is unable to travel through solids, but it can travel through liquids and gases.
There are two properties of light. The first property of light is called reflection. Reflection is when light bounces off a surface which then allows the object to be visible to the eye. For example, when the moon is seen in the sky, it is because the light from the sun reflects off the surface of the moon. A light ray comes off a surface at an equal angle to the angle at which it struck the surface.
The second property of light is called refraction. Refraction is when a ray of light passes from a transparent medium to another transparent medium such as from air to water, it changes speed and the way it bends.
For example, when a pencil is placed into a glass of water, the pencil will seem like it is broken into two pieces. Because the light is traveling through the water, there is refraction, and the light bends causing the pencil to look like it is in two pieces. Another example of refraction, is the use of eyeglasses to improve a person's vision. Using a glass that is curved at a certain angle the vision of a person is corrected by the way light is refracted in the eye.
All sounds are different, but one thing in common is that sounds are created by something that vibrates. Sound wave vibrations can travel through solids, liquids, and gases. Sound waves travel through solids much faster than through liquids or gases, and faster in liquids than gases.
The molecules that make up a solid are closer together allowing the sound to travel faster. Molecules are the substances that make up solids, liquids, and gases. In a liquid, the molecules are farther apart, so the sound waves travel slower. In a gas, the molecules are spread farther apart so the sound waves travel much slower. A sound traveling through a solid can be better heard than traveling through a gas.
For example, a vibrating speaker collides with the molecules in the air passing along the energy and creating sound waves. This is why music can be heard from the speakers. When there are no molecules in the air, like in space, the sound could not be heard. The speed of sound travels much slower than the speed of light. It normally travels in air at about 1200 feet per second.
In summary, light and sound is everywhere. Light is a form of energy we can see when it is reflected off the surface of an object. Sound is a mechanical vibration that can pass through solids, liquids, and gases. Reflection and refraction are two properties of light. Sound travels through solids much faster than through liquids and gases. Molecules, which make up all objects, are closer together in a solid allowing the sound to travel faster. Light travels much faster than sound.
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