Category Every Day Science

Look at a picture of yourself. Now look at it from a different angle. Do you see another side of yourself in the picture? No, but if you were looking at a hologram you could walk around the picture and see the left side of your body, your back, your right side, your front, and the top of your head.

A hologram is an image that looks three dimensional-that is, it seems to have depth, height, and width. Some credit cards have holograms on them. Holograms also appear in advertisements, artwork, and jewellery.

A hologram is made with laser beams. A laser beam is a kind of coloured light. One laser beam is bounced off a mirror then off the subject and onto a special film. Another laser beam is also bounced off a mirror and onto the film. Where the two beams cross on the film, they make a tiny pattern of bright and dark stripes, a hologram.

Guiding a laser beam onto the film will produce light rays that seem to come from the original subject. The resulting three dimensional image appears to hover in space. You can look over, under, and around the subject. When a hologram is viewed with regular light or sunlight, the image appears with rainbowlike bands of colour.

To make a hologram of an object, such as this teddy bear, a laser is aimed into a mirror then at the object. Another laser is reflected off a mirror and then onto the film. The film records the hologram.

 

Picture Credit : Google

Is a DVD the same thing as a CD? Although DVD’s looks like CDs, they are different. A DVD works like a CD, but it can hold more information. A CD usually records only sound, but a DVD records pictures as well as sound.

Each side of a DVD can contain two layers. Each of these layers can store data. CD’s have only one layer of information.

Before CD’s and DVD’s were invented, people used cassette tapes and videotapes. Cassette tapes record and play sounds, and videotapes record and play sounds and images.

Cassette tapes, videotapes, CD’s, and DVD’s can be played again and again. That’s one of the reasons people like them so much.

A DVD can be played in a DVD player. A DVD player is often connected to a television set. When a DVD is played, pictures appear on the TV screen and sound comes out of speakers.

 

Picture Credit : Google

Cassette tapes sound good when they are new. But after a while, they start to sound scratchy. A compact disc, or CD, produces much better sound. It is played using a special light called a laser beam. Only the beam of light touches the CD, so it stays like new.

Sound is stored on a CD in a digital (numerical) code-a string of 0’s and 1’s. When a CD is made a microphone turns sound vibrations into electrical signals. Then a machine changes the signals into a digital code.

This code is fed into a powerful laser. As a blank disc turns, the laser cuts billions of tiny pits that represent the digital code into the surface of the disc.

Inside a CD player is another, less powerful, laser. When the CD is played, the laser reads the position of the pits. The laser reads from the centre to the edge of the disc as the CD turns. These pulses of light are turned into electrical signals. The signals make the speakers vibrate. Then you hear the sounds.

Inside a CD player, a laser beam shines on a mirror and through a lens onto the pits on the CD. When the beam hits a pit, the light is scattered. When it hits between pits, the light is reflected straight back. A sensor reads the patterns of reflected light and turns the patterns into electrical signals. These signals are used to produce sounds.

 

Picture Credit : Google

You probably don’t think of a toilet as a machine. But that’s what it is. You press down the flush lever, and the toilet does the work.

Most toilets have two main parts-a tank and a bowl. The tank sits on the back of the toilet bowl. Both contain water. The bottom of the tank has an opening with a plug. The plug keeps the water in the tank from flowing into the bowl. Pushing down the lever to flush the toilet lifts up the plug.

Water then rushes out of the tank. It flows into the toilet bowl through small holes all around the rim of the bowl.

The fresh water pushes the dirty water into the drainpipe. The plug closes when the tank is empty. Fresh water then flows through an inlet tube into the tank. And the tank is ready for the next flush.

 

Picture Credit : Google

With a hairdryer, we don’t have to wait for our hair to dry.

Inside the hairdryer, electricity travels on a pathway of wire. The electricity travels easily on most of the wire in the pathway. This is called conducting electricity. The path is open. The electrons in the wire are free to move.

But some metals resist, or slow down, the electric current flowing through the hairdryer. When the electrons slow down, they bump into one another as they move through the wire.

Then the wire heats up. The harder they bump and push, the hotter the wire gets.

When you plug in a hairdryer and turn it on, electricity travels through it. It powers a tiny fan. Then the electricity travels to coiled wire made of resistant metals. These wires heat up. The fan blows heat from these wires out through a vent. This is the hot air that dries your hair.

Inside an electric hairdryer, there is a coil of wire that heats up. The fan blows the heat out to dry your hair.

 

Picture Credit : Google

Brrrrahhhh! It may sound like a roaring monster, but it’s only a vacuum cleaner doing its dirty work. The noise comes from an electric motor that runs a fan. The fan helps the vacuum cleaner suck the dirt up the hose and into the bag.

When you turn on the vacuum cleaner, the fan starts. It draws air from the bottom of the vacuum cleaner up into the dust bin or bag. As the air moves up, it leaves an empty space at the bottom of the vacuum cleaner. Any empty space is called a vacuum. That’s how the vacuum cleaner got its name.

A brush at the bottom of the cleaner helps loosen dirt in the rug. This brush is called a beater brush. A rubber belt connects the brush to the motor. As the motor spins, the brush spins and makes the rug vibrate. The vibration loosens the dirt. The vacuum pulls more air and dirt into the dust bin or bag.

When the dust bin gets full, it needs to be emptied. Or, when the bag gets full, it needs to be thrown away and replaced with a fresh bag.

 

Picture Credit : Google