Show NORMAL DEPARTMENT DEPARTMENT- ft I. I SUGGESTIVE PLAN Reflection and Refraction of Light ADAPTED TO GRADE III HI MOTIVE To To present conditions that will lead the child to discover that light reflects from surfaces on which it falls that light in passing from one medium to another is bent out of its ts course Pedagogical Principle The The child through self-effort self forms an image which is the basis of his judgment Materials Large Large rectangular bottle crayon dust mirror glass spoon prism penny candles pasteboard box and screen LESSONS 1 AND X 2 We shall darken one of the cloak rooms What do you se see 7 I shall now now admit a ray of light into the room What do you see I shall darken th the room again and instead of admitting a aray J al ray of light I shall bring into the ro room room m ma a book What do you see now Why is it we can see a a ray admitted into tI- tI this this i darkened room and cannot see the book From what does the ray of light come Sun Such a body we call luminous The book a non-luminous non body What is the he greatest luminous body N Name am other luminous bodies Also name some non-luminous non bodies Is this wire luminous or non luminous Let us heat it red hot and again darken ou our room room What does the wire do now What kind of an object is it How can we make it non-luminous non again I shall shaH darken the room again and admit a ray of light distributing a little crayon dust through the air by means means means' of blackboard erasers What do you see What do you notice about that ray of light Let us take this piece of white te linen line thread l and stretch it tightly throughout the length of the sunbeam I Does the thread follow the path of df f the sunbeam at every point Then a beam of light that enters a room takes what course We shall now make a hole in a card and look through it a at t a candle We shall then make another similar card and move the cal card caid d till we can see seethe seethe the flame through both at once In how t many positions is this possible We will then try with three or four cards when we have succeeded with two 1 shall have little blocks with grooves in which to place the cards What do you notice about the holes in the cards Why is it that light will shine through these pin-holes pin only in this position What does this tell us about rays of Ii light You will now draw on blackboard the apparatus we used to show that a ray of light is iss is s LESSON III We shall again admit a ray into our darkened room If there should chance be no sun I shall use a candle placing it inside of a pasteboard box in order to obstruct all the rays save one which will be admitted into the room through a pin pin hole Here is a mirror or as you would say a looking glass I place placeit it it for the beam to look in What do you you see It strikes it as a ball What does it do then Bounds off again Where To the wall What about the light as it bounds off from the mirror It moves in a straight line When it reaches the wall how does it look What do you see on the wall I turn the mirror What does the beam do It turns too I turn it again What do you notice That whenever the mirror is moved the beam is moved too What t did you notice about itc path Its path patha a K is always a straight line But when the light first looked into the mirror what did you notice The light bounded off This bounding off we call reflection 4 4 The probabilities are that in connection l i k it f I. lt i f Ir r with these first three lessons the que question ques- ques ques 1 1 tion II Why Why the the ray of light makes makes- a a around ai i 1 r round und spot on n the floor wall etc wi willbe will willbe l be asked To show why this is so I Ishall I Ishall shall use a little box the lid of which has been replaced by tissue paper I Ishall Ishall shall make a pin pin- pin hole hole in the bottom of box and hold it in front of a very small small- bright gas flame The gas flame can then be traced on the tissue paper Then I shall try the same experiment with the ray of light from th the sun an and we sha shall l compare the images LESSON IV On our table in the darkened room letus letus let letus us place instead of a mirror a piece of tin a cup of water a saucer of ink a abright abright abright bright button a piece of china successively successively successively in the ray of light What did you notice That these acted much as the mirror did What was each of these objects able to do to the light To alter the direction of the ray or in other other- words lords to reflect it I take a handful of flour and gently sprinkle it in the ray of light What do you see The tiny bits of flour roll round and over as they fall much as the dust did the other day and turn the light in every tion How do these little particles of dust act They act just like little reBec- reBec tors I hold a piece of drawing ling paper in inthe inthe inthe the ray What do you notice immediately immediately tely That it does not act as the mirror How dc do you know Because we canno cannot trace the rays from the paper In this case we say the light is diffused I hold a black piece of paper in the ray What do you notice now That we can only see the paper with difficulty The black paper seems to swallow up the rays or in other words absorb the light and hence as we see it with difficulty difficulty difficulty culty it reflects a very little light Which of these objects seemed t to illuminate the room the most Which i next Which seemed to illuminate the room only a little Which seemed to i or t t t ff 4 1 fI c illuminate it least of of all What have i you found out about abou light That light is reflected from all objects What objects reflect the most light Polished surfaces surf aces LESSON t I We shall again darken the room and 5 admit a ray of light This time we shall hold a clear glass tumbler filled with water in the ray of light The ray lights it up just sufficiently to be seen in the darkened room I add a teaspoonful of milk to the water and stir it well We Wethen Wethen Wethen then hold the tumbler of milk and water in the ray of light How does the tumbler look now How does the room look Do you believe we could s see e to read Before we put milk into the water how did the room look After we put milk into the water the room became light How do you account for that How did the small particles of milk act Did the tumbler appear bright on all sides Why The little particles catching the light reflected it itin itin itin in every direction Some of the little particles turn the light in one direction and then in another Can you think of anything that acts just in that way The dust and tiny little specks in the air Let us place this screen between us usand usand usand and the candle in our darkened room What do you see now The wall Why Do you see the lamp How is it that we cannot see the lamp and yet see the wall How is it that I can see you and other things about us on opening the shutters The light of the sun falls upon you and the various objects round roundabout roundabout roundabout about and bounds off some of it striking striking ing ng our eyes How do you see the trees How do you see the blackboard LESSON VI d. d A written lesson on bl blackboard LESSON VII In this jar of water Jet let us place this stick What do you see Are you very sure it looks bent Let us take it out L. L again and exa examine ine it to see if the stick is perfectly straight Let us put it in again It still stin looks bent I put in a ruler The ruler is bent too Where is isit isit isit it bent Did you never dip the end of ofa a sti stick ck into a pond or lake If you pass passa a pond on your way home from school you nJ might try it Those that have done doneso so tell us how the stick looked to you The stick looked as if it were broken This appearance is called refraction or breaking Let us put this penny in an empty empty- basin Now stand back until you see just a bit of the edge Stand perfectly still and keep your eye on the edge while I gently pour in some water What do you see The penny seems to be rising out of its place and moving towards me I shall pour in a little more II Now I see all of it quite plainly How does the bottom of the basin look to you As though it had risen Could that be Could the water r raise Jise the penny No but the penny looks as though it had risen just as the stick did when it looked bent in the water We shall now draw these experiments on the blackboard LESSON VIII We shall again darken our room and admit a ray of light I shall choose the largest sided flat-sided bottle I can find and cover it with black paper with the exception of one ne side Through a papered side I shall cut a long slit and fill the bottle half full of water We Ve Wethen Wethen then reflect our beam of light to the thelong thelong thelong long slit by a mirror What do you see Where does the ray bend What causes the ray to bend Are water and air different different different differ differ- ent things We call air one medium and water another Then what do you notice as the ray passes from one medium into another The rays of light from the penny and stick started from what medium i Into what medium must they have passed to reach our eyes What happened to the rays as they left the medium water and passed assed into the medium air That is why the penny and stick seemed to be he raised in the water We shall now draw on the blackboard this experiment showing the directions of the ray in passing from air into water LESSON IX Did you notice the beautiful rainbow several evenings ago You may tell us how it looked In what part ot of the sky did you see it Was the sky clear or cloudy in that part Where was the thes s sun sun n What time in the evening did you see see it Was it raining when you saw it What color was on the outside of the bow What color next to red Orange was between what colors f t Name all the colors you you saw in the rainbow How many colors in all Let us darken our room again and admit a ray ray of light Let Letus us pass this ray through this three-cornered three piece of glass Tell us just what what you see What do you see on the wall What do those colors make you think of From what did all those colors come From the ray of light What separated them thus From what did all the colors in the rainbow come What separated them th as we saw them in the rain rainbow bow several evenings ago What little prisms do you suppose were used We shall now paint the colors After painting the colors we shall hold holda a convex x lense in the refracted sun sunbeam beam What do you tou see now How many colors are in the white spot Nellie Craft CM j. j MI x D Director of Science Teaching in Tra Training z zu School f Jr |