Light and Sound

1. Light and Sound 4th Grade Science

2. EQ: What is light? It’s a kind of energy called “electromagnetic (EM) radiation” (but this kind of radiation is not harmful). There are other kinds of EM radiation too (radio waves, microwaves, x-rays, etc.), but light is the part WE can see, the part that makes the rainbow.

3. How does light travel? • FAST and STRAIGHT • About 186,000 miles per second , so light from the sun takes about 8 minutes to go 93 million miles to earth. • If you could DRIVE to the sun at 60 mph , it would take you 177 years to get there! In one second, light can go around the earth 7 times!

4. How are shadows formed? • When light strikes an object, some light reflects. When there is an obstacle in the way of the light, and it cannot pass, there is no light to reflect, and thus a shadow is formed. • A SHADOW IS FORMED WHEN LIGHT SHINES AT AN OPAQUE OBJECT BLOCKING THE LIGHT RAY CAUSING A SHADOW BECAUSE LIGHT ONLY GOES IN A STRAIGHT LINE.

5. Vocabulary •  Transparent object is one that lets light pass through.   (clear window) • Translucent objects lets some light go through but not all  (bathroom window) • opaque: light can not go through it. Impenetrable by light; neither transparent nor translucent. Example: opaque object lets no light pass through-( table) • absorption: refers to the physical process of absorbing light. The process in which incident radiated energy is retained without reflection or transmission on passing through a medium.  For example, light can not go through an object that is opaque because that object absorbs the light.

6. Refraction • http://ilovenewton.com/wp-content/uploads/2012/05/interference_refraction_reflection-300x225.jpg

7. Sound energy •  Sound is a type of energy made by vibrations. When any object vibrates, it causes movement in the air particles. These particles bump into the particles close to them, which makes them vibrate too causing them to bump into more air particles. This movement, called sound waves, keeps going until they run out of energy. If your ear is within range of the vibrations, you hear the sound. • Pitch: the frequency at which an object vibrates to create a sound. A tuning fork, for example, that vibrates 440 times a second will produce a perfect “A” note. It is these predetermined levels of frequencies that pitch is categorized into the twelve chromatic musical tones.

8. vibrate:   move back and forth rapidly. • Did you hear that sound? It was made by air vibrating. The same is true for sounds made by musical instruments. The difference between NOISE and MUSIC is that musical sounds are organized into patterns that have pitch and rhythm. Noise is just random, disorganized sounds. Sounds are made and travel in the same way whether they are musical sounds or noise. • A musical sound is called a tone, and is produced by air vibrating a certain number of times per second. These vibrations are called waves.

9. EQ: What is sound? • Sound is a form of energy, just like electricity and light. Sound is made when air molecules vibrate and move in a pattern called waves, or sound waves. • Think of when you clap your hands, or when you slam the car door shut. That action produces soundwaves, which travel to your ears and then to your brain, which says, “I recognize that sound.” • This is from Science Kids at Home.

10. SOUND • Sound is a type of energy made by vibrations. When any object vibrates, it causes movement in the air particles. These particles bump into the particles close to them, which makes them vibrate too causing them to bump into more air particles. This movement, called sound waves, keeps going until they run out of energy. If your ear is within range of the vibrations, you hear the sound. • Picture a stone thrown into a still body of water. The rings of waves expand indefinitely. The same is true with sound. Irregular repeating sound waves create noise, while regular repeating waves produce musical notes. • When the vibrations are fast, you hear a high note. When the vibrations are slow, it creates a low note. The sound waves in the diagram show the different frequencies for high and low notes. • Low frequency notesHigh frequency notes

11. Low Frequency Notes

12. High Frequency Notes

13. Quiz • The bending of a wave caused by the change of speed that occurs when the wave passes from one medium into another is __________. 2. The bouncing back of a wave off an object or surface is ______________.

14. 3. Describes materials that let nearly all the light rays that hit them pass through _______________. 4. Describes materials that let some light rays pass through but scatter some of the other rays is ________. 5. Describes materials that do not let any light pass through them ______

15. Directions: Put a T for true and an F for false • ___ Light is electromagnetic radiation. • ___ Opaque objects can either absorb or reflect light. • ___ Transparent substances reflect light. • ___ A convex lens is curved outwards. • ___ A prism is a type of lens • ___ You can see your reflection on an opaque object • ___ The visible spectrum is light you can see. • ___ All light passes through translucent objects. • ___ A concave lens is like the inside of a sphere. • ___ Refraction means the light stops.

16. answers: • T • T • F • T • F • F • T • F • T • F