light - science4fun

The telescope is an instrument that allows us to see the distant objects closer. We can view objects that are far beyond the range of our eyes.

This instrument had opened the new door for us to study the space from the Earth and changed our understanding of the universe. With the help of a telescope, it was proved that the Earth revolves around the Sun and the old geocentric concept was dropped.

First Telescope

Telescope is one of the instruments that was not invented by a scientist. Instead, it was invented by a Dutch eyeglass maker Hans Lippershey. While working with lenses.

He brought two lenses in front of each other and found that distant objects were seen closer through them. Then he fitted two lenses (a convex and a concave) in a tube and made the first working telescope. His telescope magnified the distant objects about 3 times. He had applied for the patent but officials said to him that this instrument is too simple to copy, and they didn’t issue the patent.

Galileo Galilei

Galileo-Telescope — Galileo Galilei’s Telescope

A great scientist Galileo Galilei when heard about this new invention. He started to build his own telescope, without ever watching the Dutchman’s instrument. He made an improved version of the telescope which magnified the distant object 8 times.

With further improvements, he made another telescope with a power of 20. He turned his telescope to the sky and watched the planets, and their moons. He proved that the Earth and all planets in solar system revolve around the Sun. Galileo continued to improve his telescopes and made one with the power of 100, which helped him to study the sky further.

There was a limit in further increasing the magnification of telescope because it decreased the field of view, combined with spherical and chromatic aberration. So, there was need of completely new kind of telescope that can eliminate these problems.

Reflecting Telescope

Isaac Newton found that the telescopic effect can also be obtained using the mirrors instead of lenses, and he made the first reflecting telescope. These telescopes were called reflecting telescopes or Newtonian telescopes because they used the reflecting power of the mirror to reflect and focus the light. Using mirrors greatly increased the power of telescopes. All the new powerful telescopes were built using the reflecting mirrors and lenses were used in smaller telescopes.

Again the restriction arrived in the further development of the telescope. No matter how much powerful a telescope is, it never gave the clear view of the sky because of the atmosphere. Our atmosphere is filled with a lot of dust and moisture that absorb the light coming from space causing the blurred view of telescopes. For this reason, scientist always dreamed about a telescope that could be brought to space.

Space Telescope

The Breakthrough came in the 20^th century when scientists sent the first telescope Known as “Hubble Space Telescope” into space in the year 1990. This telescope orbits 600 km above the Earth. With this new telescope, scientists discovered a lot of new galaxies. They acquired a deep understanding of the universe that was not imagined before it.

Today electric lights have become the important and highly used appliance in our daily lives. We need it for lighting our houses, building and streets etc. Today we have handheld portable lights that can provide a backup time of more 12 hours. The technology that we use today may be different from the past, but what we have today starts back from the invention of the Incandescent light bulb.

Early developments

The efforts to make a working light bulb went back to 1800. When an Italian scientist named “Alessandro Volta” during his experiments on the development of electric battery observed that, when a copper wire between the terminals of the battery is connected, it starts to glow due to the passing of electricity.

The first approach in the development of light bulb was made by Humphry Davy in 1802. When he connected the terminals of the battery to a carbon electrode (used as a filament), it started to glow. This glow didn’t last longer because filament burnt very quickly. His invention is known as “Electric arc lamp”.

Researches and developments on the light bulb were continued by many inventors. Some historians say that the light bulb was invented by 20 inventors before Thomas Edison, but no one was able to make an affordable and durable (long-lasting) design of the light bulb that can be brought into the market.

Thomas Edison – The First Practical Light Bulb

The Main problem in the developments of the light bulb was the filament (a conductor that emit light inside a light bulb), it didn’t last too long and melted in a short duration of time. Thomas Edison was very serious in the development of light bulb.

He started developing and testing new filaments that could last longer. He tested many materials including carbon, platinum, and other metals. He had developed a carbonized filament that lasted for 14.5 hours. Which proved him, he is going to the right way. He continued developing the filament that can last much longer. He had tried more than 3,000 designs of the light bulb and 6,000 different materials for the filaments.

Finally, he found that carbonized bamboo filament can last for more than 1,200 hours continuously. So, Edison used the carbonized bamboo filament in his light bulbs.

Thomas-Edison-Light-Bulb — Thomas Edison’s Light Bulb

Edison became successful not because he had developed a durable filament, but he developed the whole system of electric lighting including the sockets and buttons for the light bulb. Also, he made world’s first power generating station in 1882.

Other inventors further improved the light bulbs and developed more durable filaments. Later, Edison’s filaments were replaced by these new filaments. Modern incandescent light bulbs use tungsten filaments, due to their high melting point.

Electricity is the source of energy that is widely used by the peoples around the world. Today, life can’t be imagined without electricity. We use it all the time for lighting our houses, powering smartphones and computer etc. You have to just push a button and you have the electricity powering your appliances. So, what is the electricity itself? First, we have to understand about the atom and its components to understand the electricity.

Atom – Basic Building Block of Elements

Atoms are smaller particles of matter, so small that millions of them can fit on the tip of a needle. These atoms are not fundamental particles, but they are made up of even smaller particles known as electrons, protons and neutrons. Protons and neutrons are held together in the center (nucleus) of an atom. Whereas, electrons orbit around the center at very high speeds. Electrons carry a negative charge and protons carry a positive charge, but neutrons are neutral (charge less). Both electrons and protons have the same amount of charge. Also, the number of electrons and protons are equal in an atom, which makes the atoms neutral (charge less). Read more about Atom

Since electrons are not bound to one location like protons and neutrons. Instead, they revolve around the center of an atom, so they can be freed from an atom by applying some force. When electrons jump to other atoms throughout the material by some applied force, they create electricity. Therefore you can consider the flow of electrons as electricity, but electricity can also be stored where electron don’t flow. So, Electricity is divided into two types, one is current electricity and other is static electricity.

Current Electricity

Current electricity is the continuous flow of electrons known as “electric current” between atoms in a closed path. The path that is followed by electrons is known as “electric circuit”. The electric circuit needs to be closed for the electric current to flow; e.g. when you push a button to power on a light bulb, you are actually closing the circuit (completing the path for electrons)through which electrons flow to power your light bulb.

Closing the circuit does not mean that electric current will always flow, electric current needs a kind of push known as “electric potential” to go around the circuit. Electric potential is measured in volts, which is supplied by electric utilities to your house at around 120 volts or 220 volts depending on your country.

Static Electricity

Static electricity is the stored form of electricity. It doesn’t flow but can be made to flow in the circuit. Static electricity is made when electrons jump from one substance to other, creating the charge imbalance between them. A substance where electrons jump becomes negatively charged because it has now more electrons than protons, and the substance from where electrons jumped becomes positively charged because it has now fewer electrons than protons. This charge imbalance creates an electrostatic force between the two substances and static electricity is created between them. For example, when you comb your hair, a charge imbalance is created between your hair and the comb. Which creates an electrostatic force between them. That is why your hair are attracted to comb when you bring hair near it.

Static electricity can be converted into current electricity by connecting two substance through a path. Have you ever seen a lightning bolt striking the ground? That was actually static electricity converted into current electricity through the path provided by air.

Rainbows are one of the beautiful masterpiece of nature. When they appear during rain they catch everybody’s attention by their beautiful seven bands of color in circular arc shape. Rainbows have inspired many artists and writer from centuries and many fairy tales were mainly inspired by them.

Rainbow presents demonstration of dispersion of light and it is evident that visible light is composed of different wavelengths which are associated with a unique color (spectrum of visible light). To see a rainbow sun must be at your back and rain falling in front of you.

Bending of Light

Rainbow is generated because of two physical phenomena refraction and reflection. When sunlight enters in a rain drop it refracts and cause dispersion of white sun light into its basic colors (like a prism do) because different colors of light refract at different angles, then these rays are internally reflected from boundaries of rain drop and again refract out of rain drop and hit the observer’s eyes. Countless rain drops refract and reflect sunlight the net effect is the rainbow.

Rainbow Color Bands

As we observe the rainbow we see it has wide color bands, as if different rainy areas disperse only single wavelength color. So how rainbow actually shows wide color bands? Actually each raindrops in the rainbow only reflect one color of light depending on altitude from the observer to understand this we will take only two colors red and violet and two raindrops raindrop A and raindrop B placed at different altitudes in the atmosphere.

When sunlight disperses and reflects in raindrop A only red light comes out to the direction of observer’s eye. Other colors comes out in lower angles and don’t reach to observer’s eye so the observer can’t see them.

Raindrop B is much lower in altitude in the sky and at that position only violet light comes out at correct angle to reach the observer’s eyes.

All raindrops that surrounds raindrop A bounce red light and those which surrounds raindrop B bounce blue light. All the raindrops that are between raindrop A and raindrop B bounce light of different color according to their position. So that way observer sees full spectrum of colors

Want to get pleasure from natural rainbow colors? But you don’t want wait for rain. By knowing science you can. In this home experiment, we are going to make a rainbow on a paper by applying the same principle that a real rainbow follows. Except that, our homemade rainbow won’t be an arc.

Things You Will Need

Small size mirror
Frying Pan (or any other similar to it)
White paper and Sunlight

How to Make

Fill the frying pan with water.
Clean the surface of the mirror and place it in the pan at an angle below the surface level of the water.
Place your pan in sunlight, such that sunlight falls on the surface of the mirror.
Hold a white paper above the pan to catch the reflected rays of the mirror.

If your setup is correct, then you should be able to watch rainbow colors on paper. If not, try to change the angle of the mirror in the pan until you see colors.

I have taken some picture on my paper and on my hand.

Watch the video of Rainbow on paper below

How to Works

When you shine sunlight on the mirror, light first enters into the water and refracts (bends). Since sunlight is a mixture of visible colors each color has its own frequency and wavelength. So, these colors refract at different angles and get separated from each other. These separated colors are reflected from the mirror on the paper.

Try it

Try using a large mirror in the water tub and note the results. Does it affect the formation of the rainbow?