Sound - Propagation Of Sound Waves In Different Mediums
Transcript
00:00hi kids today we will learn about sound so let's get started sound is a
00:11vibration that can be heard by a human or animal ear sound is created when
00:21something vibrates and faster the vibration louder the sound like when the
00:29sticks hit the drum head drum head vibrates and produces sound waves even
00:38when we speak our vocal cords vibrates because of which sound is produced so
00:46every time we hear a sound it's because of some vibrations that produce some
00:53sound waves which reach our ears so kids cause of sound is a vibration and it can
01:02travel through air water liquids and even solids see can sound travel through
01:10air take two spoons and bang them together you hear the sound it shows
01:20that sound travels through air
01:26as there is only air between the source of sound and your ear now let's see can
01:34sound travel through water when you are underwater or when someone's swimming
01:41under the water he or she can hear all the sounds coming from the poolside
01:51so it shows that sound can travel through water rather sound travels
01:58faster in water than in air divers can listen to every sound that is coming
02:05from outside the water this shows that sound waves can travel through water now
02:14let's see if sound can travel through solids if someone knocks at the door
02:22from outside the person inside the room can listen and there is a solid object
02:31that is a door between the source of the sound and the ear so it shows that sound
02:37can travel through the solids if there is any loud noise outside the room you
02:46can hear the sounds that are coming from outside the room that shows sound can
02:51travel through solids now let's have a look at a simple activity you can also
02:59perform the same just need a friend of yours for this activity and a table place
03:06your ears at one end of the table that can be wooden or metallic now ask your
03:14friend to tap on the table with his hands on the other side of the table you
03:20will find the sound much louder in the ear which is placed on the table it
03:26shows that sound travels much faster in the solid medium than in air friends
03:35till now we learned that sound waves originates when something vibrates like
03:41vibration of a string of a guitar when it's locked vibration of our vocal chords
03:48when we sing or speak vibration of door when someone knocks it every sound wave
03:57originate when something vibrates now let's see how this sound wave propagates
04:06or moves any vibration causes the molecules in the object vibrate which in
04:14turn vibrates the molecules in their adjacent medium like when a door is
04:21knocked molecules of the door vibrate and they in turn vibrate molecules in
04:28the air and this vibration passes on to the next and next molecules and this way
04:37sound travels from the door to the listener sound waves always need some
04:45medium to travel medium can be air liquid or solid and denser the medium
04:55faster the sound waves travel in the vacuum there is no matter so sound waves
05:03cannot travel at all in the vacuum now we will see why do sound waves travel
05:11faster in denser mediums gases or air is the least dense medium and sound
05:20travels with least speed in air solids are the densest mediums so the sound
05:28waves travel fastest in solids distance between particles in solids is very small
05:36and so particles can pass the vibration to next particle very quickly and so
05:43sound waves travels fastest in solids liquids are less densely packed so sound
05:52travels second fastest in liquids and air is the least dense medium so sound waves
06:02travel with least speed in the air or any gas
06:09so friends today we learn about sound we will learn more about sound in the next
06:17section now you may go ahead and take a quiz to learn more bye-bye