Light For Beginners (1960)

[Music] have you ever helped your mother on wash day as penny is doing today it's a fine sunny day the light from the sun is very bright Penny can feel some of the heat that comes from the Sun as it shines on her face she can look about the yard and see the tree with its green leaves and the dog house and her dog too because of the sunlight nearly everything looks bright and colorful but there are other days when the sunlight isn't as bright then colors aren't as bright either the tree looks darker today the dogghouse seems to be a darker color too things aren't bright today because clouds keep much of the Sun's light from shining through later in the day just before the sun set there is even less light the dog housee is harder to see without much light on it before very long it's night we can't see very well who is in the yard it's Penny's father we can see his face as he lights a match now as he lights a fire the Flames give even more light but far less light than the sun does we call the light from a fire artificial light because it doesn't come from the Sun can you name some other ways to make artificial light what about a flashlight a flashlight will make one kind of artificial light it is electric light the light near the back door is electric light too light made in different ways is much alike whether it is from a light bulb or from a fire or from the Sun or from these auto headlights all light is much alike because it is so much alike light often does the same things all light can travel from one place to another light from the auto headlights travels to the door of the garage we can see clearly the part of the garage that the light is traveling to we can see Penny's father only while he is in the light when he goes out of the light we can't see him in the morning we can see the garage very well because there's much more light from the sun our Earth receives light from the sun because light can travel through space light travels through many things it travels through glass windows made of glass let light into Penny's house light travels through this plastic Bowl too but not as much light travels through this plastic as through window glass we can see Penny's hand but not as clearly as if the light were coming through glass but light doesn't travel through some things such as a person's hand when light doesn't travel through something we often see a shadow here is a shadow made by the sunlight Penny remembers that Shadows can also be made without sunlight in the dining room we'll see some Shadows made with artificial light we can use a flashlight to give us light first first we'll turn off all the electric lights in the room to make it dark now we can see the light from the flashlight that travels to the wall there's a shadow it's the shadow of a pair of scissors light can't travel through the scissors to the wall we can tell that the scissors are stopping part of the light because the shadow on the wall is shaped just like the scissors when we take the scissors out of the light there is no shadow Nothing is Stopping the light from traveling to the wall but Penny's hand will stop part of the light we can see the shadow of her hand where light is not reaching the wall now we're going to learn another thing about light that light travels in a straight line to show this we'll use the flashlight and some black tape to stop part of the light traveling from the flashlight we also need a straight ruler and a small mirror now the flashlight has been taped so that light coming from it can travel only through a narrow opening in the tape we'll turn the flashlight on and turn off the room lights when the flashlight is held near the wall we can see a long line or beam of light on the wall by holding a straight ruler along the edge of this line we can see that the edge of this beam of light light is straight The Edge stays straight even when the line moves up or down have you ever seen a straight edged beam of light such as this you have if you've ever watched a beacon at night watching this Beacon we can see clearly that the beam of light travels in a straight line much as this beam does on the wall in Penny's house by using a mirror we can change the direction in which light travels light travels to the mirror and then upward from the mirror in a New Direction when light changes its direction in this way we say it is reflected when the mirror moves the reflected light changes Direction let's look at another example of reflected light perhaps you've set the table for a meal as Penny often does and you may have seen how a shining knife reflects light sunlight travels to the shiny silverware the silverware changes the direction of the light and we can see it reflected to the wall we saw how a mirror changes the direction of light whenever light changes its direction in this way it is reflected light the light does not travel through the mirror but it will travel through this magnifying glass we turn the glass so the light will travel through it as the light travels through the magnifying glass the beam of light is bent or changed in shape we call light that is bent in such a way refracted light a special piece of glass called a prism will also show refracted light a prism will bend sunlight in a special way on the table we see many colors because sunlight is being bent by the prism here's another way to show refracted sunlight instead of a glass prism we can use a pan of water and a mirror we pour a little water into a flat pan we set a small mirror against the edge of the pan in the water when the mirror is slanted just right on the ceiling you'll see many colors just as you do in a rainbow if you've ever seen a rainbow you've seen a very good example of refracted light do you remember some of the things we've learned about light we've said that all light is much alike in many ways whether it is sunlight or artificial light we also learned that all light travels from one place to another light travels in a straight line but we can change the direction in which light travels then we see reflected light sometimes we can change the direction in a special way if we do this we'll see that light is made up of all the colors of the rainbow we call this refracted light light is most important to us because without it we couldn't see because light travels light from the electric light will help us to see at night as it travels to our book and other things in the room because light travels in a straight line auto headlights help us to see the road ahead at night during the day light is useful too because the direction in which light travels can be changed we can see things behind us without turning around by using a mirror to change the direction of light because light travels through many things such as the colored glass in this traffic light we can see the Stop and Go signals even during the day we found out some important things about what light can do perhaps now you can think of more ways in which we make use of the things light does [Music]