Category Science

You even looked at yourself in a funfair mirror. Did it make you laugh? You may look very short and fat or very tall and skinny. Funfair mirrors are curved. Curved mirrors bend light different from flat mirrors. Bent light makes the image that is reflected look different, too.

Who is that person in the mirror? It seems to be another you, doing exactly what you are doing. How can a mirror “copy” you?

A mirror is very smooth. The front of a mirror is made of flat, polished glass. Behind the glass is a thin layer of silver or some other kind of shiny material.

As you stand in front of a mirror, light bounces off you and passes through the glass. When the light hits the shiny layer behind the glass, it bounces straight back at you. This is why you can see yourself.

Your reflection is a good copy of you. But have you ever noticed that your reflection does the exact opposite of what you do? If you hold out your right hand, your reflection holds out its left hand. Each part of you makes the opposite part of your reflection in the mirror.

What do you think will happen if you print your name and hold it up to a mirror? Try it and see.

Picture Credit : Google

A full moon gives enough light for a game of hide-and-seek or for an evening walk. Where does the bright, silvery light of the moon come from? You might be surprised to learn that it comes from the sun! The moon shines only because the sun shines on it. Some of the sun’s light is reflected, or bounced off, the moon and hits the earth. So what we call “moonlight” is actually reflected light from the sun.

Some of the things we see—light bulbs, neon signs, traffic lights, and even television tubes—are like the sun. They give off light. But most of the things we see are like the moon. They have no light of their own. Light from the sun, or a lamp, or something else shines on them. They reflect that light into our eyes, and the reflected light tells us the shapes, sizes, and colours of these things.

Turn off the light in your room one night. If there is no light from a lamp or a window to bounce off things, you cannot see them. Everything is dark. When the lights are turned on, reflected light shows us what is there.

Picture Credit : Google

In the sunshine, your shadow travels everywhere with you. Sometimes it bends in funny places. And sometimes it bends into a strange shape. But as long as the sun shines, your shadow is always there. On a very cloudy day, or in a dark room, you have no shadow at all. Where does your shadow go? What is your shadow?

We have shadows because light moves in a certain way. It moves in waves, something like ripples in water. As long as nothing is in the way, the light waves move in one direction. But when the light waves hit an object, they are stopped. Then, on the other side of the object that stopped the light waves, there is a dark space – a shadow.

Objects in a dark room have no shadows because there are no light waves travelling through the room. On cloudy days, shadows are harder to see because the clouds break up the light waves from the sun. The clouds soak up some of the light waves and scatter the rest of the light waves in all directions. When the light waves scatter and bounce instead of moving in one direction, no shadows are formed.

Picture Credit : Google

Sleepily, you open your eyes. Sunlight is streaming through your window. It is time to get up and start your day.

The sunshine lit up your room and woke you. But the light from the sun does much more than that. It makes life on the earth possible.

Sunlight gives us energy. This energy heats the earth so that animals, plants, and people can live. It also makes green plants grow. All the food we eat comes from plants or from animals that eat plants.

Light is so important that people have invented ways to make it. We have candles, torches, electric lights, neon signs, and lasers. All these things help us to see. But light does other things, too.

The sun is the source of all heat and light energy on Earth. Aside from the obvious benefits of solar energy, and aside from our obvious knowledge that the sun is the source of all food on earth, how much direct or indirect sun does the human body need to survive.

We know that all plants require a certain amount of sunlight to make food and survive, through a process called photosynthesis. We know that animals get their energy from the food they eat. However, animals would not have a food source, if it were not for the sun. For example, some animals that live deep underwater, where no sunlight exists, but they feed on organic matter (dead plants and organisms that sink to the ocean floor from the surface). This organic matter contains energy that was first produced by the sun.

Humans get our energy from the food we eat, and all of that food is derived from the energy of the sun. So, we need the sun to survive. But do humans need direct exposure to sunlight to survive, not counting our food and heat sources?

A study published in the Archives of Internal Medicine, stated that humans need sunlight for vitamin D. The study shows that those with the lowest vitamin D levels have more than double the risk of dying from heart disease and other causes over an eight-year period compared with those with the highest levels of vitamin D.

Do you know that some people fly on a bag of hot air? Of course, the “bag” is a huge hot-air balloon. A balloon filled with hot air can lift people.

When air is heated, its molecules speed up and begin to push on one another. This makes the air expand, or take up more space. The molecules of hot air push further and further apart until only a few molecules take up a great deal of space.

The molecules of hot air that fill a balloon are further apart than the molecules of colder air outside the balloon. So the hot air weighs much less than the colder air. Because the hot air is lighter, it rises. It pushes up inside the balloon. When the push is strong enough, it lifts the balloon high into the sky.

Ask a grown-up to heat a toaster. Standing I metre away from the toaster, blow soap bubbles so that they float above it. Watch the bubbles rise as they reach the hot air above the toaster! Be careful not to get the toaster wet! Electricity and water are dangerous together!

A burning candle has a soft, glowing flame that gives off light. But when you turn on a light bulb, there is no flame. So how does a light bulb give off light?

When the light is on, electricity runs through a tiny wire inside the bulb. This makes the wire hot. Like everything else, the wire is made of tiny bits of matter called atoms. As the wire in the light bulb gets hot, the atoms soak up energy. Pretty soon, the atoms have soaked up all the energy they can hold. Then they begin to throw off the extra energy as light.

Compact fluorescent lights or lamps (CFL’s) are twisted glass tubes filled with gas. CFL light bulbs give off light when electricity passes through the gas, causing the tubes’ coating to glow.

Some bulbs produce light when electricity flows through tiny devices called light-emitting diodes (LED’s). LED’s are used in remote controls, billboards, traffic lights, street lights, and even car headlights.