QUESTION: How does a computer use its memory?
A computer has four main parts. It has a central processing unit or 'brain'. It has an input that feeds in data (usually linked to a keyboard), and an output unit that produces finished work (for example, as a print out on paper). The fourth and the vital part is the memory unit, where the computer stores the information it needs to carry out its work. The computer stores this data as electrical charges on magnetic disks.
QUESTION: How do bar codes work?
In asupermarket, the checkout assistant 'reads' each item in your troley electronically by scanning the pattern of black and white stripes marked on the package. This pattern is the bar code, containing information which is passed automatically to a main computer, recording each item sold.
QUESTION: What is light?
No one really knows what light is made of. In the 1600s Sir Isaac Newton thought light was made up of bullet-like particles which he called corpuscles. The Dutch scientist Christian Huygens thought light was made up of pulses, or waves, travelling through space. Modern science has found truth in both theories. Light certainly does travels in waves, but it also behaves as if it were made of particles. Scientists now call these light particles photons.
Light is a form of energy, similar to heat. It is the only type of energy we can see. Light comes from a start such aas the Sun and travels trough space. Stars shine as a resilt of their immense nuclear energy.
QUESTION: How does light travel?
Light travels at enormous speed, at roughly 300,000 kilometers a second (186,000 miles a second). At this speed, the light from the Sun still takes more than eight minutes to reach the Earth. The speed of light was first measured accurately in 1676, by Olaf Roemer of Denmark. Nothing travels faster than light.
QUESTION: What makes a light bend?
Light is bent when it is bounced back from a surface, such as mirror. This bending is called reflection. Light is also bent when it travels from one transparent surface to another. This bending is called refraction. It explains why a pencil standing half in and half out of water looks broken.
QUESTION: What makes the colours of the rainbow?
The rainbow is a nature's spectrum. Falling drops of rain behave like tiny prisms. They break up white sunlight into the colours of the spectrum. The first person to show that white light is a mixture of colours was Sir Isaac Newton. Between 1665 and 1666, he carried out experiments in a darkened room. He put a glass prism in a beam of sunlight streaming trough a small hole in the wall, and saw it split into the colours of the rainbow : red, orange, yellow, green, indigo and violet. When he placed a second prism in the coloured beam, he saw the light rays bend back and become white again.
QUESTION: Why do mirrors reflect our images?
Everything reflects light but most surfaces are rough, so the light is diffused or spread in all directions. A mirror's smooth, shiny surface reflects light much more accurately as parallel rays so giving a clear image.
QUESTION: When was the first photograph taken?
The earliest known photograph was taken by the French scientist Joseph Niepce in 1826. It was made on an asphalt-coated pewter plate, and shows a view from a window. The exposure took eight hours.
In the 1830s and 1840s two new photographic processes were developed. They were the daguerreotype of the Frenchman L.J.M. Daguerre and the calotype of the Englighman W.H. Fox Talbot. The Daguerreotype used a silver-copper plate instead of glass. It took a minute to expose the plate. In 1888 the American George Eastman invented the Kodak camera, which used rolled films instead of plates.
QUESTION: Who discovered X-rays?
The German scientist Wilhelm Roentgen discovered X-rays by accident in 1895. He was experimenting with a cathode ray tube and noticed that crystals in the same room glowed when the tube was switched on. Even when he moved the crystals to the next room, they still glowed. Roentgen realizedf that invisible rays were causing the glow. The rays could even penetrate solid walls. he called them x-rays (X = unknown).
QUESTION: How radar was invented?
Radar was invented in the 1930s. It worked by transmitting a radio beam from the gorund. Any object crossing the beam (such as an aircraft) produced an 'echo', and this could be recieved on the ground and used to work out the height and position of the aircraft.
QUESTION: How did the laser get its name?
The first laser was made in 1960 by an American scientist, Theodore H. Maiman. Its name caomes from a set of initials that stand for a Light Amplification by Stimulated Emission of Radiation. A laser produces a powerful beam of light so powerful it can burn a hole through metal. Unlike the light from the torch, a laser beam spreads hardly at all.
