But, the fact is that we are living in the middle of a plethora of waves. Whatever we hear and whatever we see is possible only due to some form of wave motion. As a matter of fact, the waves do not stop with visible light and audible sound. What scientists found out is that the total spectrum of light goes into a larger, invisible range of electromagnetic (infrared and ultraviolet, microwave and x-ray waves) and sound extends to ultrasonic range that are not audible to humans. Interestingly some animals like dogs can hear such sounds!!

Let’s try to get into this strange world of light and sound –

What is light made of?

This is not an easy question. Light has no mass and is not really considered matter. So does it even exist? Of course it does! We couldn’t live without light. Today scientists say light is a form of energy made of photons. Light is unique in that it behaves like both a particle and a wave.

Why does light go through some things and not others?

Depending on the type of matter it comes into contact with, light will behave differently. Sometimes light will pass directly through the matter, like with air or water. This type of matter is called transparent. Other objects completely reflect light, like an animal or a book. These objects are called opaque. A third type of object does some of both and tends to scatter the light. These objects are called translucent objects.

Light helps us to survive

Without sunlight our world would be a dead dark place. Sunlight does more than just help us see (which is pretty great, too). Sunlight keeps the Earth warm, so it’s not just a frozen ball in outer space. It also is a major component in photosynthesis which is how most of the plant life on Earth grows and gets nutrients. Sunlight is a source of energy as well as a source of vitamin D for humans.

The speed of light

Light moves at the fastest known speed in the universe. Nothing moves faster than (or even close to) the speed of light. In a vacuum, where there is nothing to slow it down, light travels 186,282 miles per second! Wow, that’s fast! When light travels through matter, like air or water, it slows down some, but it’s still pretty fast.

To give you an idea as to how fast light is, we’ll give you some examples. The Sun is almost 93 million miles from the Earth. It takes around 8 minutes for light to get from the Sun to the Earth. It takes around 1.3 seconds for light to go from the moon to the Earth.

Refraction

Normally, light travels in a straight path called a ray, however, when passing through transparent materials, like water or glass, light bends or turns. This is because different materials or mediums have different qualities and different densities.. In each type of medium, whether it is air or water or glass, the wavelength of the light will change, but not the frequency. As a result, the direction and speed of the traveling light wave will change and the light will appear to bend or change directions.

One example of refraction is a prism. Prisms are unique in that each color of light is refracted to a different angle. So it can take white light from the Sun and send out light of various colors.

Lenses use refraction to help us see things. Telescopes help us to see things far away and microscopes enable us to see very small things. Even glasses use refraction so that we can see everyday things more clearly.

Sound

Sound is a vibration, or wave, that travels through matter (solid, liquid, or gas) and can be heard.

How does sound move or propagate?

The vibration is started by some mechanical movement, such as someone plucking a guitar string or knocking on a door. This causes a vibration on the molecules next to the mechanical event (i.e. where your hand hit the door when knocking). When these molecules vibrate, they in turn cause the molecules around them to vibrate. The vibration will spread from molecule to molecule causing the sound to travel.

Sound must travel through matter because it needs the vibration of molecules to propagate. Because outer space is a vacuum with no matter, it’s very quiet. The matter that transports the sound is called the medium.

Speed of Sound

The speed of sound is how fast the wave or vibrations pass through the medium or matter. The type of matter has a large impact on the speed at which the sound will travel. For example, sound travels faster in water than air. Sound travels even faster in steel.

In dry air, sound travels at 343 meters per second (768 mph). At this rate sound will travel one mile in around five seconds. Sound travels 4 times faster in water (1,482 meters per second) and around 13 times faster through steel (4,512 meters per second).

What is the Sound Barrier?

When airplanes go faster than the speed of sound (also called Mach 1), it’s called breaking the sound barrier. Most airplanes don’t go this fast, but some fighter jets do. When they pass through the speed of sound, the airplane sheds water drops that have condensed on the plane creating a cool looking white halo (see the picture above).

When planes break the sound barrier they also create something called a sonic boom. This is a loud noise like an explosion that is generated from a number of sound waves that are forced together as the plane is now traveling faster than sound.

Volume

The volume of sound is the measure of loudness. To quantify volume we use decibels. The more decibels, the louder the sound is. A soft sound, like a whisper will measure around 15-20 decibels. A loud sound like a jet engine is more like 150 decibels. The threshold of pain occurs at around 130 decibels.

Loud sound can actually damage your ears and cause loss of hearing. Even sounds as loud as 85 decibels can ruin your ears if you listen to them over a long period of time. For this reason, it’s a good idea to not listen to loud music or have your headphones turned up too loud.

Did you know?

Here are some interesting facts about sound and light –

• To measure the depth of sea, we use sound wave technology. Sonar (originally an acronym for sound navigation ranging) is a technique that uses sound propagation (usually underwater) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels.

• Nothing can travel faster than light. As per Einstein, if an object with finite rest mass will start approaching the speed of light, it would become infinitely heavy which is not possible.

• If we say that an object is 5 light minutes away, we actually see its image which was 5 minutes ago. Therefore, the stars (which are very far away from our planet) we see at our skies are actually their images of hundreds and even millions of years ago.

It is not even 150 years when James Maxwell confirmed that electricity and magnetism were not different forces – they were one. The view was initially suggested by Oersted and then reinforced by Faraday and Maxwell proved it through experiments.

This unification of two major forces has been a watershed in science. It not only gave rise to a lot of applications that we use extensively today but also led to understanding of nature of light and to the birth of quantum physics.

Electromagnetism, as a unified concept, showed easy conversion between the 2 forces of Electricity & Magnetism.

Electromagnetism

An electric current flowing through a wire can produce the same effect that magnet can produce.

The magnetic effect of a current was first observed by a Danish Physicist called Hans Christian Oersted.

– He observed that a magnetic compass needle showed deflection when it passed through a wire carrying current

– Thus, a current-carrying wire behaves like a magnet and carries a magnetic field around it .This is also the magnetic effect of an electric current. The direction of the deflection of the needle changes if the direction of the current is reversed by connecting the wire into reverse terminals.

– This property of an electric current is used to change magnetic materials like soft iron into magnets by passing electricity through them. This is used widely in various applications.

Electromagnet

When an electronic current flows through a wire, it generates a magnetic field. This is an important concept in electricity. The magnetic field can be increased by coiling the wire. This allows more current to flow through a smaller distance and increases the magnetic field.

Right-Hand Rule

When current is flowing through a wire, the magnetic field rotates around the wire. The direction of the current determines the direction of the magnetic field. You can figure out the direction of the magnetic field using the “right-hand rule”.

To determine the direction of the magnetic field, look at the picture above. Take your right hand and point your thumb in the direction of the current (I). Now wrap your fingers around the wire. Your fingers will point in the direction of the rotation of the magnetic field (B).

Motors

One of the important applications of electromagnetism is the electric motor. An electric motor converts electrical energy into physical movement. Electric motors generate magnetic fields with electric current through a coil. The magnetic field then causes a force with a magnet that causes movement or spinning that runs the motor.

Electric motors are used in all sorts of applications. There are even several electric motors inside your computer including one to turn the fan, one to open and shut the CDROM drive, and one to operate the hard drive.

Electromagnetic Induction

Another important application of electromagnetism is induction which was found my Michael Fraday Induction is when movement is used to create electricity (the opposite of using electricity to create movement which we normally see in daily life ) As a wire is moved through a magnetic field, current will begin to flow through it.

Hence , Electromagnetic induction is the production of voltage or electromotive force due to a change in the magnetic field.

Electromagnetic induction can be generated in two ways, namely when the electric conductor is kept in a moving magnetic field and when the electric conductor is constantly moving within a static magnetic field. When Faraday moved a bar magnet through an electric coil, he noticed a change in voltage of the circuit

Generators

Electric generators convert mechanical energy into electrical energy using induction. As a coil of wire is spun between two opposite magnets, an electric current is generated that can be used to power electronic devices.

Generators can get their power from a wide variety of sources. Two popular electric generators of renewable energy include hydropower and wind power.

Electromagnetism Facts!

Some electric generators can be driven by human power such as a hand crank or a bicycle to generate electricity.

Loudspeakers use Electricity & Magnetism or electromagnetism to vibrate the cone and produce sound.

Using electromagnetism, powerful magnets can be turned on and off using electricity, unlike permanent magnets.

For science videos : https://www.youtube.com/c/ExperiHub?sub_confirmation=1

For more Science related blogs  : https://experihub.com/did-you-know/

Some forces are obvious and some we can just imagine being there. When we pick an object, we need to apply a little force. But why do we need to put in effort to pick an object? Because, there is an invisible force that is pulling the object towards the earth and we need to overcome that force by applying a counterforce. Or when we drive a car, we need to overcome the counterforces of friction and air resistance that pulls us back.

Can you imagine that if there is no friction and no air resistance and if we kick a ball, there will be no reason for the ball to stop and it would go round the earth again and again (assuming that it does not get hit by a tree or something that blocks its way)? Actually, we will need to stand out of its way or else it might hit us from the back 😊

So, one thing is certain. We are dealing with forces all the time and they are all around us and there is no way to escape them (actually, as you would have realized, it’s good that we can’t escape them). So, let us look at how scientists look at them.

What is force?

In physics, force is a push or pull on an object. A force can cause an object to accelerate, slow down, remain in place, or change shape.

How to Measure Force

The unit of measure for force is the newton which is abbreviated as “N”. One newton is the force needed to accelerate one gram of mass by one centimeter per second squared. Other units of force include the dyne and the pound-force.

Examples of force

Force, Mass, and Acceleration

Force can be figured out if you know the mass and acceleration of an object. This equation comes from Newton’s Second Law of Motion:

f = m * a

Where f = force, m = mass, and a = acceleration.

Forces and Vectors

Force not only has a magnitude (which is what we get in newtons when we use the equation above), but it also has a direction. This makes force a vector.

Vector, in physics, a quantity that has both magnitude and direction. It is typically represented by an arrow whose direction is the same as that of the quantity and whose length is proportional to the quantity’s magnitude. Vectors are shown by an arrow that indicates the direction of the force and a number that indicates the magnitude.

Forces in Equilibrium

Sometimes there can be many forces acting on an object, but the object remains still. In this case the forces are in equilibrium. The sum of the forces, or the net force, is zero.

The picture below shows an object sitting on a table. The object isn’t moving. This is because the force of gravity pulling the object down is equal and opposite to the force of the table pushing up. The net force is zero and the forces are in equilibrium.

weight as a force acting on an object

Combined Forces

When multiple forces are acting on an object, the resultant force is the sum of the vectors of the individual forces. We won’t get into complex vector math here, but take for example a tug of war. The two sides are each pulling. If one side is pulling with a force of 2 N in left direction and the other side is pulling with a force of 3 N in the right direction, then the resultant force is 1 N in the right direction.

Some of the forces we encounter

Friction – Friction is a force caused when one object rubs against another. It works in the opposite direction of the main force.

Gravity – Gravity is a force caused by a large body, such as the Earth. Gravity pulls objects toward the Earth with an acceleration of “g” which equals 9.8 m/s2.

Electromagnetic – Electromagnetic force is a force associated with electric and magnetic fields.

Nuclear – Nuclear forces are the forces that hold atoms and their particles together.

Tension – A pulling force that is exerted by a string, cable, or chain on another object.

Elastic – An elastic force is a force exerted by an object trying to return to its natural length. This is modeled by a spring that has been pulled by an external force but is pulling back while trying to return to its original length.

Trivia

Galileo Galilei, an Italian scientist, was born before Newton and he is often called “the father of modern physics” and “the father of modern science.”

Newton’s first law of motion was based on Galileo’s formulation of the concept of inertia. Galileo stated that an object in a state of motion possesses an “inertia” that causes it to remain in that state of motion unless an external force acts on it.

Galileo was a supporter of “heliocentrism”, an astronomical model where the Sun is the center of the solar system with the Earth and other planets revolving around it.

This was against the prevailing belief at that time that Earth is at the center and everything revolves around it. Church was opposed to Galileo’s findings and found them blasphemous and put him under house arrest for eight years during the later portion of his life. His period of house arrest occurred between 1634 and 1642, during which time he wrote a book before becoming blind. The book contained the summary of his life’s work, science of motion and strengths of materials. He named the book – “Two New Sciences.”

From pre-historic times, man keeps finding ways that will help him simplify his life. As a cave man and a hunter, humans discovered fire and ways to ‘create’ fire. Fire helped him be safe from predators and improved the taste of food that he could now cook. As a nomad, man realized that rotating friction is less compared to sliding friction. A wheel was invented. 

Simple Machines are various tools and techniques that make human life easy. Pulleys, levers and hammer are examples of some simple machines. Most of the complex machines are composed of many simple machines put together. Can you think of how many simple machines are used in making a car or an airplane? 

Just to illustrate, if we look under the hood of a car, we will see – 

– fuel carburetor based on Bernoulli’s theorem

– steering wheel that helps rotate the steering rod

– gears to switch the available power between thrust and speed

– clutch plates using friction to transmit power

– brake shoes using friction to control the vehicle

– transmission mechanism using bevel gears to change the direction of rotation from that of the transmission rod to that of the wheels

– spark plugs (petrol engines) to convert heat to mechanical energy

& the list goes on and on!

Go to a manufacturing plant, research lab or an amusement park – we are always surrounded by a lot of equipment that are all made up of a large number of simple machines. 

Hollywood movies project that machines might overtake humans one day. With the advent of “intelligent machines” this might no more be just fiction. 

However, whatever the future may hold, it is fascinating to see how simple concepts that we study in our middle school shape up to make such complex systems.