Good Morning! Grandma is typing up May 23 of the Calendar History here and the experiments on Light from Book (12). Grandma forgot to mention that she will be typing up some more experiments for the Summer and Her Books she is using on separate blogs as well as finishing the material from Patricia. Look for it later into next week. For now we will finish these experiments and the school season history.
May 23 1707 Carolus Linnaeus, Swedish botanist and founder taxonomy, was born. Book (1) says under Plant classifications, "Have your (children) look up the word taxonomy in the dictionary. Then encourage them to walk through their (neighborhood) to observe flowering plants, writing careful notes of the specimens they find. Have them use these observational records and their research skills to find the scientific names of their plants.(see if they are edible and good for what things)
In 1734 Dr. Franz Mesmer, German physician who developed a treatment called mesmerism, which is the basis of the word mesmerize, was born. In 1824 Ambrose Everett Burnside, American Civil War general whose whiskers on the side of his were called Burnsides and later sideburns, was born. Then in 1910 Margaret Wise Brown, children's author, was born. Book (1) says, "Margaret Wise Brown wrote stories about feeling lonesome, getting lost, and acting naughty or silly. She wrote more than 100 books in her career, some published under the pen names Golden MacDonald, Timothy Hay, and Juniper Sage. Have your (children) each write a story using one of the topics Brown often wrote about. Then have them choose their own pen names. Why did they select a particular name?
The events start with 1785 In a letter, Benjamin Franklin wrote about his new invention, Bifocal Eyeglasses. In 1788 South Carolina became the eighth state. In 1873 Canada established the Northwest Mounted Police.
In 1903 Eleven-year-old William Frederick Price became the Youngest soldier to enlist in the British Army in this century. In 1984 C. Everett Koop, the U.S. surgeon general, said there was solid evidence that Nonsmokers can suffer Long Damage from Inhaling Other People's Cigarette Smoke. In 1989 An Italian interior designer named Stefania Follini Climbed out of the Cave in Carlsbad, N.M., in which she had spent the previous 130 days.
We will finish the line for May starting Monday. I may get it to you sooner.
The experiments on Light from Book (12) are as follows:
Bore a hole in the middle of the base of a box. Stretch parchment paper over the mouth of the box and secure it with a rubber band. If you focus this simple camera on a brightly lit building from a dark room, the image appears upside down on the screen.
Our eyes work on the same principle. The light rays fall through the pupil and lens and project an inverted image on the retina. The image is turned the right way up again in the sight center of the brain.
Bore a hole about one fifth of an inch wide in a strip of metal and smooth the edges. Bend the metal so that you can fix it with adhesive tape half an inch above the bottom of a thin glass. A pocket mirror is placed inside on a cork, so that it is on a slant. If you dab a drop of water into the hole, you can see small living organisms and other things through it, magnified by up to fifty times.
The drop magnifies like a convex lens. When you bring your eye near to it the sharpness can be adjusted by bending the metal inwards. The angle of the mirror is adjusted automatically by moving the glass.
Fire through ice
You would hardly believe it, but you can light a fire with ice! Pour some water which you have previously boiled for several minutes into a symmetrically curved bowl, and freeze it. You can remove the ice by heating slightly. You can concentrate the sun's rays with the ice as you would with a magnifying glass and set thin black paper alight, for instance.
The air in fresh water forms tiny bubbles on freezing and makes the ice cloudy. But only cooled imperceptibly when they pass through the ice.
Look from just above the rim of a bucket of water, and dip a spoon upright into it. The spoon seems to be considerably shorter under the water.
This illusion is based on the fact that the light rays reflected from the immersed spoon do not travel in a straight line to your eyes. They are bent at an angle at the surface of the water, so that you see the end of the spoon higher up. Water always seems more shallow than it actually is because of the refraction of light. The American Indians also knew this. If they wanted to hit a fish with an arrow or spear, they had to aim a good deal deeper than the spot where the fish appeared to be.
Lay a penny in a cup near the side. Place the cup in oblique light so that the shadow of the rim just covers the coin. How can you free the penny from the shadow without moving the cup or the coin or using a pocket mirror? Quite simple! Bend the light rays back to the coin. Fill the cup with water and the shadow moves to the side. The light rays do not go on in a straight line after striking the surface of the water, but are bent downwards at an angle.
Half fill a glass with concentrated salt solution and top it up with pure water using a spoon. If you hold a pencil at the side of the glass, it seems to be broken into three pieces.
The light rays coming from the immersed pencil are bent at an angle when they emerge from the water into the air at the side of the glass. Because salt solution has a different composition from pure water, the angle of refraction is different. We know that how much light rays are bent when they pass from one substance into another entirely depends on the 'optical density' of the different substance.
Cloud of gas
If you pour some bicarbonate of soda and vinegar into a beaker, carbon dioxide is given off. You can normally not see the gas, but if can be made visible: tilt the beaker with its foaming contents in front of a light background in sunlight. You can see the gas, which is heavier than air, flowing from the beaker in dark and light clouds.
Carbon dioxide and air have different optical densities, and so the light rays are bent when they pass through them. The light clouds on the wall are formed where by refraction the propagated light is bent towards it, and the dark clouds are seen where light is bent away.
Look through a round jam jar filled with water. If you stand a pencil a foot behind it, its image appears doubled in the jar. If you close your left eye, the right-hand pencil disappears, and if you close your right eye, the other goes.
One sees distant objects reduced in size through a normal magnifying glass. The water container behaves in a similar way, but since it is cylindrical, you can look through it from all directions. In our experiment both eyes view through the jar from a different angle, so that each one sees a smaller image for itself.
Secret of 3-D postcards
Draw red and blue vertical lines a short distance apart and lay over them along their length a round, solid, transparent glass rod. You can see both lines through the glass. But if you close one eye the red line disappears, and if you close the other eye the blue line disappears.
Each eye looks from a different angle through the rod and perceives-by the particular angle of light refraction-only one line. The experiment explains how the stereoscopic postcard works: its surface consists of thin, transparent ripples, which behave like our glass rod.
Two photographs, each taken from a different angle, are copied together in very fine vertical strips to give a picture, so that under each individual ripple lies a strip of one and a strip of the other photograph. In the ripples we see, as with our glass rod, only the strip of one photograph with each eye, and the brain finally joins the images to give a 3-D picture.
Glue a funnel together with smooth silver paper, as shown in the picture. Stick your finger into it, point it to the midday sun, and you will feel it warm up quite a lot.
The sun's rays are reflected from the walls of the funnel to the middle and are concentrated on the central axis, which is formed by your finger. If you put your finger into the dismantled concave mirror of a bicycle lamp, the son's rays would be unbearably hot. In this case they converge at a point, the focal point of the concave mirror, at which the bulb is usually placed. The heat produced is so great tat one could easily start a fire with a concave mirror. (Grandma is wondering if the heat would enter the hole on the other side and heat the inside of a circle outward this way.)
The sun's radiation can be caught in a bowl and by means of the heat potatoes can be stewed in their own juice. A 'nourishing' joke and an instructive experiment at the same time. Take a soup bowl or a large salad bowl with as small a base as possible and line it inside with household aluminum foil-bright side outwards. (Grandma thinks of an old electrical night light used for working on cars at night for this.)
Smooth the folds with a rubber ball and a spoon until the foil acts like a mirror. Split it a little at the base of the bowl so as to be able to press in a suction hook, on which you fix a small raw potato. If you point the cooker on a warm day towards the midday sun, the potato becomes hot at once and is cooked after some time.
Now and then you must re-align the bowl towards the sun. The sun's rays falling on the aluminum foil are reflected to the middle and concentrated on the potato. In tropical countries people often use concave mirrors for cooking. Did you know that even electricity can be produced in large poser stations by the son's radiation?
If you place a jar over a coin lying on the table, it looks just as if it were in the jar. If you now pour water into the jar and put the lid on it-abracadabra!-the coin has disappeared, as if it had dissolved in the water.
When the jar is empty the light rays from the coin travel into our eyes in the usual way. But if the jar is filled with water, the light rays do not follow this path any more. They are reflected back over the bottom of glass when they hit the water from below at an angle. We call this total reflection, and only a silvery gleam can be seen on the bottom of the jar.
View into infinity
Hold a pocket mirror between your eyes so that you can look to both sides into a larger mirror. If you place the mirrors parallel to one another, you will see an unending series of mirrors which stretch into the distance like a glass canal.
Since the glass of the mirror shines with a slightly greenish tint, some light is absorbed at each reflection, so that the image becomes less sharp with increasing distance. Nevertheless the experiment is interesting, because one can make an image of infinity for oneself.
You need a highly glazed picture postcard. Cut the edges smooth and divide the writing side along its length into four panels an inch wide. Scratch the lines lightly and bend and stick the card into a triangular tube-shape with the glazed side facing inwards. Both openings are glued up with transparent cellophane. At one end also stick white paper over the cellophane, having previously inserted small snips of coloured cellophane in between, so that they can move easily. A beautiful pattern, which alters on tapping with your finger, appears in the tube.
The tree highly glazed surfaces of the bent picture postcard behave like mirrors and multiply the image of the coloured pieces of cellophane. A polished surface reflects better, the flatter the light rays hit it. But since part of the radiation is absorbed into the surface, the image reflected from it is not so clear and bright as with a mirror.
Obtain three sections of mirror each about 3 x 4 inches in size, or cut them your self. Polish them well, and join them with adhesive tape-reflecting surfaces facing inwards- to make a triangular tube. Stick coloured paper outside. If you now look obliquely from above into the mirror prism you will discover a magic world! If you hold a finger in the prism, its image is always multiplied six times in an endless series in all directions. If you place a small flower inside, a meadow of flowers stretches into the distance. And if you move two small figures, innumerable couples dance in an immense hall of mirrors.
Stick a pin with a polished head into a cork cut in half length ways and fix some celluloid on it to protect your eyes. If you look at the tiny light reflection from the head of the pin under a bright lamp, while holding it right up to the eye, it appears as a plate sized circle of light. A hair stuck onto the moistened celluloid is seen magnified to the width of a finger in the circle of light.
The head of the pin behaves like a small convex mirror. The light which hits it is spread out on reflection, and irradiates a correspondingly large field on the retina of the eye.
Cut out four pieces of aluminum foil 1 X 1 1/2 inches in size. If you use the silver paper from a cigarette packet, you must remove any backing. Stick the sheets on to a match like the blades of a mill wheel, with the bright sides all facing in the same direction. Blacken the matt sides over a candle, holding a knife blade behind the foil to assist you. Put a drop of glue at one end of the match, draw it out to a hair-fine thread and let it dry. Place a tall jar in the sun, hang the mill inside, and it soon begins to turn without stopping.
We know that dark surfaces are more strongly heated by sunlight than light ones, and such heat difference is the secret of the light mill. The sooty side of the foil absorbs the light rays and is heated about ten times more strongly than the light-reflecting bright side. The difference in the amount of heat radiated from the sides of the blades causes the rotation.
The sun's spectrum
Lay a piece of white paper on the window sill and place on it a polished whiskey glass full to the brim with water. Fix a postcard with a finger-wide slit onto the glass, so that a band of sunlight falls onto the surface of the water. A splendid spectrum appears on the paper, and the bands red, orange, yellow, green, blue, indigo and violet can be easily distinguished.
The experiment is only possible in the morning or evening when the sunlight falls obliquely. It is refracted at the surface of the water and the side of the glass and is separated as well into its coloured components The experiment also works well with light from an electric torch.
Spectrum in a feather
Hold a large bird's feather just in front of one eye and look at a burning candle standing a yard away. The flame seems to be multiplied in an X-shaped arrangement, and also shimmers in the spectral colours.
The appearance is produced by the bending of light at the slits. Between the regular arrangement of feather sections (vanes and barbs) are narrow slits with sharp edges. The light is bent on passing through them, that is, it is refracted and separated into the spectral colours. Since you see through several slits at the same time, the flame appears many times.
You will certainly only have seen a rainbow in the sky as a semi-circle up to now. You can conjure up a complete circle for yourself from sunlight. Stand out-of-doors on a stool in the late afternoon with your back to the sun and spray a fine shower with the water hose. A coloured circle appears in front of you!
The sunlight is reflected in the drops so that each shines with the spectral colours. But the colours of the drops are only visible to your eyes when they fall in a circular zone at a viewing angle of 85° in front of you. Only the shadow of your body briefly breaks the circle.
Cut a circle about four inches in diameter from white cardboard and colour it as shown with bright-coloured felt pens. Stick the disk on a halved cotton reel, push a pencil stump through it and allow it to spin. The colours disappear as if by magic, and the disk appears white.
The colours on the disk correspond to the colours of the spectrum of which sunlight is composed. On rotation our eyes perceive the individual colours for a very short time. However, since the eyes are too sluggish to distinguish between the rapidly changing colour impressions, they merge and are transmitted to the brain as white.
Look alternately left and right at the blue of the sky. You will not trust your eyes because it flashes continuously with bright lightning.
What is the explanation for this appearance? If you look at the picture, it is imprinted on the retina of the eye. But red colour impressions remain longer on your retina than blue when you move your gaze. So the impression of the red lightning is overlaid for an instant on the blue of the sky. These two colours together, however, produce an impression of bright light in your brain. Since a new impression of the lightning is formed with each movement of the eye, the process is repeated.
Make a small hole in a card with a needle. Hold it close to the eye and look through it. If you bring a newspaper very close you will see, to your surprise, the type much larger and clearer.
This phenomenon is caused in the first place by the refraction of light. The light rays passing through the small hole are made to spread out, and so the letters appear larger. The sharpness of the image is caused-as in a camera_by the shuttering effect of the small opening. The part of the light radiation which would make the image blurred is held back.
Close your left eye in a dark room and hold a lighted torch close beside the right eye. Now look straight ahead and move the torch slowly to your forehead and back. After some time you will see a large, treelike branched image in front of you.
Very fine blood vessels lie over the retina of the eye, but we do not normally see them. If they are irradiated from the side, they throw shadows on the optic nerves lying below and give the impression of an image apparently floating in front of you.
Motes in the eye
Make a hole in a card with a needle and look through it at a burning, low-power electric light bulb. You will see peculiar shapes which float before you like tiny bubbles.
This is no optical illusion! The shapes are tiny cloudings in the eyes, which throw shadows on to the retina. Since these are heavier than the liquid in the eye, they always fall further down after each blink. If you lay your head on one side, the motes struggle towards the angle of the eye, showing that they follow the force of gravity.
Ghost in the castle
(This has to be in Grandma's words--If you draw a large castle with a open gate doorway in the middle on one side of a white piece of paper and put a black ghost smaller on the other side. Now stare into the mouth of the ghost for about a minute in bright light. Then look at the castle a minute, a white ghost will appear.)
When you look at the figure, part of the retina is not exposed to light from the black surface. The rest of the optic nerves are dazzled by the bright paper and tire quickly. If you now look at the castle tower, the tired optic nerves do not see the white of the paper in its full brightness, but as a grey surface. The rest, on the other hand, see the white tint of the paper all the more clearly. So an exchange of the black and white surfaces is produced and you see a white ghost in the dark arch of the tower. Only after quite a time, when the nerves have adjusted themselves, does the ghost disappear.
Goldfish in the bowl
Stare in bright light for one minute at the eye of the white fish. If you then look at the point in the empty gold fish bowl, there appears to be light green water and a red fish in it after several seconds.
If the eyes have stared for a long time at the left-hand picture, the part of the light-sensitive retina which is irradiated by the red surface tires and the optic nerves concerned become rather insensitive to red. So on looking at the white surface in the right-hand picture, they do not perceive the red radiation which is present in white light. They are only sensitive to the yellow and blue components, which together give green. But the part of the retina which has received the picture of the white fish is now sensitive to the opposite colour to green, namely red. Coloured after-images can be produced with other colours just as well. Each colour changes into the opposite; i.e. blue into yellow, yellow into blue and green into red.
(Grandma has to write this one also because you must have a picture of a magician holding a wand in his left hand facing you drawn on the left side of a black picture with a rabbit on the right.) Then shut your left eye and stare at the magic rod with your right. If you now slowly alter the distance of the picture--Abracadabra--the rabbit suddenly disappears.
The retina of the eye consists of a large number of light sensitive nerve endings, the so-called rods and cones. These are absent at one point, where they join together at the optic nerve. If the image of the rabbit thrown on the retina falls at this "blind spot" as we move the picture we cannot see it.
The disappearing finger
Cover your left eye with your right hand and look straight ahead with your right eye. Raise your left forefinger to your left ear and move it until the tip of the finger is just visible (A). If you now move your eye to look directly at the finger (B) the light rays from the finger go past it.
Hole in the hand
Roll a piece of writing paper into a tube and look through it with your right eye. Hold your left hand open on the left next to the paper. To your surprise you will discover a hole, which apparently goes through the middle of the palm of your hand. The right eye sees the inside of the tube and the left the open hand. As in normal vision, the impressions which are received by each eye are combined to give a composite image in the brain. It works particularly well because the image from inside the tube, which is transferred to the palm of the hand, is in perspective.
(For this next picture you must have a moon drawn on the left side of the paper with a little star in the middle and a rocket on the right side of the page.) Hold the picture so that the tip of your nose touches the star, and turn it round slowly to the left. The rocket flies into the sky and lands again on the moon. Each eye receives its own image on viewing and both impressions are transmitted to give a composite whole in the brain. If you hold the star to the tip of your nose, your right eye only sees the rocket and the left only the moon. As usual, the halves of the image are combined in the brain. As you turn the picture on its edge, it does not shrink any more because both eyes see the same image by squinting.
Hold your forefingers so that they are touching about a foot in front of the tip of your nose and look over the fingertips away to the opposite wall. On doing this you will see a curious ball, which is apparently fixed between the fingertips.
When you look over your fingers your eyes are focused sharply on the wall. But the fingers are then projected on the retina in such a way that the images are not combined in your brain. You see the tips of both fingers doubled. These finally combine to give the illusion of a round or oval image.
This is for the experiments today. Grandma will give the rest next week.