light - science4fun

Do you remember the movies where alien forces use laser guns in battles? Well, lasers are a very famous piece of technology. These were once considered as high-tech gadgets, but today modern science made lasers very common technology used in everyday life.

What is LASER?

A laser is just a device that emits light, but it is different from light bulbs or LEDs. So, what makes them different? The main difference is that lasers emit coherent light. So, what is coherent light? Coherent light has all its waves in phase with each other – It means their crests (upward bulges) and troughs (downward bulges) line up together. Also, the lasers emit monochromatic light or a single wavelength of light – they don’t have a bunch of colors, but only one.

So, what is special about coherence? The coherence of light allows a laser to focus on spots very tightly. Other sources of light such as light bulbs don’t give coherent light. As a result, their light is spread in all directions throughout the empty regions e.g. rooms. Furthermore, Laser’s coherence allows it to focus very precisely, which is very useful in many applications.

How Does Laser work?

The working of LASER lies in its name. The LASER is not just a name but it is an acronym, which stands for “Light Amplification by Stimulated Emission of Radiation”. Let’s understand its working step by step.

The electricity from a battery cell excites the atoms of semiconductors material inside the laser. As result, the electrons of these atoms move to higher energy level.
The electrons of excited atoms when falling back their normal level emit photons of light.
The emitted photons of light are allowed to reflect back and forth on two parallel mirrors. This results into stronger and stronger beam of light as suggested by word “amplification”.
The photons that are not able to reflect back and forth due to the wrong angle, they go back and strike the atoms again. As a result, two coherent photons are emitted – called “stimulated emission”.
The one mirror from the two reflects light partially – means it allows some of the light to pass through it. When the beam become sufficiently strong, it goes through the partial reflecting mirror and hits the spot where the laser points.

Uses of Laser

Lasers are very useful technology and it has revolutionized many fields. Some uses of lasers are discussed below.

Communication

optical-fiber-cabler-laser — Optical fiber cable with laser beam

Today we are able to access very fast internet connections. This is due to the use of optical fiber cables. Optical fibers carry the information signals in form of laser-light from one place to another. Before the use of lasers, information was sent and received as electrical signals through electrical cables.

Industry

Today, we are able to measure precisely in nano-meters (billionth of a meter), and cut the materials very precisely with the help of a laser. The other uses of lasers in industries are welding, cutting, and carving.

Electronic Goods

We use DVD players regularly to watch movies, programs, and songs. The DVD players get the data from a disc with the help of a laser. A laser points at the very fine details of a disc where the information is stored. After laser light hit the disc, some light is reflected and falls on a sensor. Then, the sensor interprets the data into an electrical signal for sending towards a TV.

The other common electronic goods that use lasers are laser pointers used by the teacher, laser pointers used in celebrations, and toys.

Medicine

Lasers are playing a vital role in today’s medicine. The main uses of laser in medicine are laser surgery of eyes, healing the skin, treating the kidney stone, cosmetics, and many more.

Weapons

on-board-navy-laser-gun — Navy on-board laser gun

Today, humans have developed very sophisticated weapons of destruction. The missiles are able to reach the target location precisely with the help of GPS and laser guidance.

Laser guns are also introduced that can make a person temporary blind from distance of few kilometers. Furthermore, the laser that can damage and destroy objects directly on the skies, oceans, or ground are under testing.

Research

Lasers are used by scientists around the world to study the atoms, stars, and other cosmic objects. The most important part that lasers play is in the field of spectroscopy. In spectroscopy, the spectra of the atoms and molecules are analyzed to find out about unknown atoms.

The other uses of lasers in the field of science are in heat treatment, weather, photochemistry, nuclear fusion, and microscopy etc.

Facts

Lasers can be used to push an object! But, you need at least 30 billion common laser pointers to a move a coin.
In 2016, Stephen Hawking announced “Breakthrough Starshot proposal”. This proposal was aimed to push a small spacecraft to space with the one-fifth of the speed of light.
Recently, scientists have discovered gravitational waves with the use of two large lasers.

Every living thing on Earth needs food to survive and live a healthy life. Plants are also living things, so they need food regularly. But instead of waiting for someone to feed them, they produce their own food. They produce their food in a process called ‘Photosynthesis’ and generate oxygen for us.

Plants need three things to make their food which are sunlight, water, and carbon dioxide. These materials are crucial for plants, they get them from nature. Sunlight from the sun and carbon dioxide from the atmosphere are available for free. But, water is available in the ground due to rain, rivers, or human irrigation system. So, getting water is a little bit difficult when rivers are dry and precipitations are very low.

How Plants Absorb Ingredients

Carbon dioxide is absorbed by leaves of the plants. The leaves of the plants contain small pores called “stomata”. The carbon dioxide is absorbed through these small pores.
Water and necessary minerals are absorbed by the roots of the plants. These absorb the water from the ground. Water is then sent to different parts of the plants through vessels in its stem.
Sunlight is absorbed by chloroplasts in the leaves of plants. Chloroplasts have a green color and those are responsible for the green color of leaves.

Process of Photosynthesis

The photosynthesis process happens in two phases in a plant.

1^st Phase: In this phase, the sunlight is absorbed by chloroplasts in the cells of plant’s leaves. The chloroplasts contain a substance called chlorophyll, which stores the energy from sunlight into a chemical called ATP.
2^nd Phase: The ATP produced in the first phase is used to produce glucose and oxygen from the water and carbon dioxide. The 2^nd phase can happen in the night time because it is not dependent on direct sunlight. This phase is also called Calvin Cycle.

Photosynthesis in terms of chemistry is a chemical reaction that is activated by light. In this reaction, light and chlorophyll break-up the water into its two constituents; oxygen and hydrogen. The oxygen and hydrogen combine with carbon dioxide to produce glucose, and oxygen is released as a gas in the atmosphere.

The glucose is like a fuel for the plants, it is used to provide energy for the growth of plants. Plants also store some glucose in their leaves, fruits, and roots to use them later.

Importance of Photosynthesis

Photosynthesis process is very necessary for all living things on Earth. It produces oxygen as a byproduct in food preparation. Oxygen is very necessary for all living things in breathing. All the oxygen on Earth has been produced by these plants and some other creatures (some algae and bacteria) since few billion years ago.

It is very difficult to predict the fate of earth without photosynthesis. But it is clear that, if photosynthesis stops suddenly, no more oxygen will be produced. Gradually, the available oxygen will be consumed and every oxygen breathing creature would die.

Besides the oxygen, plants are considered as producers of food. All the animals highly depend on the plants for their food, because animals just eat food without producing it. Some animals directly eat plants are called herbivores (e.g. sheep, and cow), and others eat the herbivores are called carnivores (e.g. lion, tiger, and dog). Carnivores are indirectly dependent on the photosynthesis.

Increasing the number of plants, taking a good care of them not only provide oxygen to us, but also provide us with food.

Fun Facts

Scientists think that first organism to use photosynthesis were cyanobacteria. They used photosynthesis about 3.5 billion years ago.
It is estimated that an adult person consumes about 740 kg of oxygen in a year. This amount of oxygen is produced by about eight trees in a year.
Our planet started to turn green after the evolution of photosynthesis in bacteria and plants.

Today, cameras have become so popular that there may be hardly any person without a camera. We all carry cameras in our smartphones that are always ready to take shots when we want. You are lucky that you are living in a time where we all carry cameras for photography.

Photography, as you know it today, was not cheap and common in the past century. Because cameras were not available in shape as we know it today.

Early cameras took hours to take a picture, which means you don’t have to move for hours! It may look strange but it is true. These cameras were only useful for taking pictures of buildings or natural scenes.

Pinhole Camera – First Working Camera

Working-of-Pinhole-camera — Working of the Pinhole Camera

History of the camera goes back to the 11^th century; a time known as the golden period of Muslims. During that period, a Muslim Arab scientist Ibn Al-Haytham – who was an expert in optics – invented the camera known as the Pinhole camera or camera obscura.

Pinhole camera was made of a wooden box that was dark from inside. This box had a small hole in it at the center of one side. When light passed through the hole it formed an inverted image inside the box. This invention was a major breakthrough in understanding how light works and form an image.

The pinhole camera was a brilliant invention and was used to form an image of the solar eclipse. This camera had only shown images when light passed through it, but it was unable to preserve the images – like we do today.

Image Preserving Camera

Nicephore-Niepce-Camera — Nicephore-Niepce Camera

Camera Obscura was used by artists for tracing the shape of an image formed inside the box. Because artists were unable to preserve the image.

The solution to the preservation of images came when Nicephore Niepce developed a paper that was sensitive to light. This sensitive paper was coated with silver chloride. When the light was directed towards the paper, it turned dark. Mr. Niepce found this discovery useful in photography. So, he performed an experiment by placing the paper inside the camera obscura where the image is formed. When he allowed the light to enter from the hole, an image started to form.

So, how an image formed on the sensitive paper that turned dark when exposed to light?

When an image is formed inside camera obscura, there are a bright light and low lights. The bright light regions turned the paper darker than low light region. This way the image was formed.

Mr. Niepce formed the world’s first photograph that was made using the light in the year 1827. This photographs took about 8 hours to form on the paper. But there was still a problem in the photograph, it was not permanent. The photograph turned dark over time due to light sensitivity.

Permanent Photograph – A Major Breakthrough

Daguerreotype-Camera — Daguerreotype Camera

Nicephore Niepce after the development of sensitive paper started to improve it so that image can be preserved for a long time. During his development, he partnered with Mr. Louis Daguerre. They both worked to somehow preserve image permanently. But during their journey to development, Mr. Niepce died in 1833. Then, the work of permanent photographs was continued Mr. Daguerre along with the son of Mr. Niepce.

In the year 1839, Mr. Daguerre found an effective process for photography, which he named after himself “Daguerreotype”. The images formed with this process were long lasting and were not affected by light.

Hand-held Cameras

Early-Handheld-Camera — Early Handheld Camera

Daguerreotype photography revolutionized the field of photography. Photography started to emerge New York City that used daguerreotype photography method.

The daguerreotype photography could only be taken inside studios because cameras were huge and took-up whole room. Also, the time for taking the photographs was still long.

The solution came after the invention of dry plates; a glass plate coated with dried gelatin emulsion. Dry plates reduced the time of image formation and the size of the camera. As a result, photographers were no longer limited to studios.

Cameras with Flexible Roll Films

camera-with-its-roll-film — Camera with its flexible roll film

The development of handheld cameras due to dry plates allowed photographers to take photographs anywhere. But, dry plates were thick and heavy, so it was still difficult for common people to buy a camera and take photographs.

The issue was solved by Mr. George Eastman. He developed flexible roll film for making negatives of the images in his camera named as “Kodak”. The flexible roll films made the camera very compact and easy to carry.

Digital Camera – Modern Cameras

Cameras with flexible roll film became very popular and were used for a long time. Then, the development of the camera further progressed and another revolutionary invention came to the digital camera. The digital cameras emerged when digital technology has sufficiently progressed.

The first true digital camera was made in 1988 and was called Fuji DS-1P. It had 2 MB SRAM for storing a digital image until the image was transferred to a computer. Despite being a successful digital camera, this model never went commercially. The first commercially available digital camera was DS-X by Fuji and was sold at the end of 1988.

Is it dark? Just light up a lamp, and you have a source of light to kick-away the darkness. Light is one of the fundamental needs of humans and every living thing (almost!). We can find our ways to home, schools, and offices because of light. Just think a bit, what will happens if the light suddenly goes away? You will be amazed that we cannot survive without light. So, what is that light?

What is Light?

It may be a bit complicated to understand, but let’s try to understand simply. The first thing to remember is that light isn’t made of matter, so it doesn’t have mass. It is just a form of energy (also called electromagnetic energy) that travels at a constant speed from one place to another and reflects from the objects. When it hits our eye, we see the objects from which the light is reflected or emitted.

So, do we really see light? The simple answer is NO!

We only see the effect of light that happens in our eyes. The light cause a chemical reaction in light-sensitive cells of our eyes. These reactions produce electrical signals that are transferred to the brain by the optic nerve.

Moreover, light is the small portion of the electromagnetic spectrum that our eye can detect. The other portions of electromagnetic radiation that you may be familiar are radio waves, infrared, ultraviolet, and X-rays etc. But, the human eye cannot detect these radiations. Our eyes are only sensitive to light, also called visible light.

Here is the complete electromagnetic spectrum

Notice, how much small portion is occupied by visible light spectrum.

How Fast Light Travel?

Visible light and every radiation of electromagnetic spectrum travel at constant speed, which is 299,792,458 m/s (meter per second) or 186,000 miles/second. It only takes 1.3 seconds for the light to reach from the moon to earth, and 8 minutes to reach from the sun.

The speed of light is the fastest known speed in our universe, and no object with mass can reach that speed. Although, material objects can reach close to the speed of light.

The interesting part!

The laws of classical physics don’t work anymore when objects reach near the speed of light. Then, comes Einstein’s theory of relativity to rescue us. This theory describes what happens when things reach closer to the speed of light.

How Do We See Colors?

The visible light not only allows us to see objects, but it also allows us to see the object in a wide variety of colors. It is because the visible light starts from the wavelength of 700nm and ends at 400nm. The colors that we can see a change from 700nm (dark red color) to 400nm (dark blue color).

Here is the complete spectrum of visible light.

The colors we see may be the single wavelengths of light or the mixture of several wavelengths. For example, the sunlight is the mixture of all wavelengths of light and we see it as white light. Just check the light spectrum image above and notice that there is no white color, it just a mixture of colors.

You can also check out our experiment: How to Make Rainbow on Paper, to confirm that sunlight is the mixture of visible colors.

Why Objects Have Different Colors?

As you know from the above discussion that, white light is the mixture of colors. So, when this white light falls on an object, it absorbs some colors of light and reflects the remaining colors to the surrounding. When our eyes catch that reflected light, it sees the object’s color that it reflected.

For example, when the light hits the green box, it absorbs all the colors of light and reflects only green color. As a result, we see it as green. Similarly, black colored objects absorb all the colors of light so we see it as black. Furthermore, the white colored objects don’t absorb any color at all, so we see them as white.

There are some materials which don’t absorb light or reflect them. As a result, we can see through these objects. These objects are called transparent objects, e.g. glass.

How Light Helps Us

The first benefit that will come to everyone’s mind is that light helps us and every organism on earth to see objects and the environment. Besides that, there many other important benefits of light, which are:

The heat from the sun reaches the earth as radiation. These radiations are absorbed by atmosphere and ground to maintain the temperature of our earth that is suitable for life. Without that heat, everything would be frozen like the planet, Pluto.
Plants use sunlight in Photosynthesis to prepare food for them and generate oxygen for us.
We use solar panels to generate electricity from light.
We are using spectroscopic analysis of electromagnetic radiation coming from space to study the far planets, stars, and galaxies.

Fun Facts

The speed of light reduces as it enters into a medium, like air, glass, and diamond.
Ants can see the ultraviolet region of light, which humans can’t see.
Ibn al-Haytham was a Muslim scientist, who first discovered that we see objects due to the light coming into our eyes. Before him, it was considered that we see because eyes emit radiations that hit surrounding objects. Ibn al-Haytham is also considered as the father of Optics (Science of light).

What is Solar Energy?

Solar energy refers to the energy from the Sun. It comes to our Earth in form of sunlight and is the widely available form of the energy. It is found at every place, where the Sun is shining. This is the energy that is available everywhere, free of cost, for everyone to use. Another term “solar power” is used, which refers to the generation of power from solar energy. Without solar energy, our Earth would have looked entirely different than it looks today. All the living things on the planet Earth are dependent on the sun.

Solar energy is a type of renewable energy because it will never run out (at least for billions of year). Unlike fossils fuels which are decreasing due to consumption, and are not renewed.

Solar energy can be converted into different forms of energy (e.g. mechanical or electrical). People around the world use solar energy for different purposes. In some places, people use solar energy for heating their homes and producing electricity for them. Many countries around the world are using solar energy to generate electricity. Among them, the largest electricity is produced by US and China.

Solar Heating

There are basically two types of solar heating methods. Each one has its own advantages and disadvantages.

Solar passive heating:
In this method, solar energy is used for heating homes and buildings by using sunlight directly. For example, houses are heated when sunlight enter through the glass windows, heating the materials inside. The heat is then trapped inside the houses and buildings, which also keep them warm during the night. Passive heating is also used in greenhouses to make them warm in the colder areas to grow the vegetables of warm places.
This method of heating has been used by humans for thousands of years ago for heating houses and drying some fruits and vegetables. The disadvantage of this method is that the things that need to be heated must be placed in the direct sunlight.
Solar passive heating
Solar active heating:
Another way to heat houses and building uses solar thermal panels. These panels collect the heat from the sun and warm up the water inside them. Cold water is circulated through these panels and then stored in the tanks as hot water. Then, hot water can be used bathrooms, kitchens, and may be used to heat the house. This method of heating is called active heating because mechanical devices are for collect, distribute and store the solar energy. It provides some advantages over passive heating. The main advantage is that the heat can be collected at one place and utilized at another place. But, extra power is needed to drive the mechanical devices e.g. water pump.
Solar active heating

Solar Electricity Generation

solar-panels-installed-house — Solar panels installed on a house

Another important use of the solar energy is to make electricity from it. Since sunlight is available everywhere, so electricity can be produced at almost every place. All the houses and buildings in remote locations can take advantage from it and may live completely independent from the grid power.

There various direct and indirect methods to generate electricity from sunlight. But, mostly used method is the use of solar cells to make electricity from sunlight. Solar cells are also known as photo-voltaic cells; these are the semiconductor devices that convert the sunlight directly into electricity. You may have seen these devices in pocket calculators and some handheld device. Solar cells can produce a small amount of power, so they are also connected together in a panel known as a solar panel to increase the amount of power.

All the houses and buildings that generate electricity from sunlight use solar panels. Solar panels are also common in the satellites because they operate far in space and they provide a source of electricity than can power than for their entire life. Recently in July 2016, a spacecraft has reached the planet Jupiter. This spacecraft generates all of its electricity from solar panels. Moreover, Mars Rovers on the planet Mars also use solar panels to power their motors and science equipment.

curiosity-rover — Curiosity – Mars Rover

Advantages of Solar power

It is the type of renewable energy and will be available for the whole life of our planet.
We can use solar panels to generate electricity in remote areas. Whereas, smaller panels can be used to power handheld devices.
They produce no pollution to generate electricity, which makes them environment-friendly.
They need low maintenance.

Disadvantages of Solar Power

Its initial cost is high.
It is available during daytime and for the night, backup devices must be used.
Backup devices such as lead-acid batteries are quite expensive.
During cloudy and rainy days, they are not effective in generating power.