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 the Necessary 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.leaves-of-a-plant
  • Water along with necessary minerals is 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.

  • 1st 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.
  • 2nd Phase: The ATP produced in the first phase is used to produce glucose and oxygen from the water and carbon dioxide. The 2nd phase can happen in the night time because it is not dependent on direct sunlight. This phase is also called Calvin Cycle.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. The 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.

growing-plantIt 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.


sun-lightIs 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?

light-speedVisible 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.visible-light-spectrum

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?

colored-balloonsAs 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

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.

  1. 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
  2. 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 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.


Solar Panel

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 – Mars Rover
Juno Space Probe

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.

TelescopeThe 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 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

Newton’s 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 20th 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.

Hubble Space Telescope

Light-BulbToday 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

Thomas Edison

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’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.