Light Measurement

There are many different units for Light Measurements. Let’s first discuss some of them.

1. Candela (cd)- It is the unit of Lumen Measurement of a light source in a specific direction, also called as candle. This intensity is perpendicular to the direction of the surface of a black body.
2. Foot candle (fc or ftc)- It is a unit of intensity which used to measure in lumens per square foot.
3. Lux (lx)-  It is the unit of illumination which equals to one lumen/ square metre.
4. End Foot candle- This unit is a measurement which is based on the focused beam only. It is a focal beam measurement from point A to point B at one-foot distance.
5. End Lumens- This measurement is based on a spot of light.


6. Luminance- Also called as Luminous Flux which is the quantity of light leaves the lamp and measured in lumens (lm).
7. Luminous (Light Level): It is the amount of light measured on the work plane in the lighted space. Remember a work plane is an imaginary horizontal, tilted or vertical line where the tasks in the space are performed.
8. Beam Lumens- It is the total flux in that region of space where the intensity is more than 50 percent of the maximum intensity.
9. Lux- It is a metric unit of measure for illuminance of a surface. One lux = one lumen/ square meter= 0.0929 footcandles.
10. Light Level- It is the measurement of intensity on a plane at a specific location known as illuminance which is measured in footcandles.
11. Efficiency—the measure of the luminous efficiency of a radiant flux which is expressed in lumens/ watt is equals to efficiency.
12. Watt- It is a measurement of electrical power which does not relate to the output level and defines as the rate of energy consumption by an electrical device in operating stage. Watts= Volts x Amps x Power Factor (PF)



The wavelength is a length of a function period which shows the distance between any two points with the same phase and measured in meter light.  Let’s discuss; ‘How to Measure Wavelength of Light’? It can calculate either from the energy or frequency by using the speed and Planck constants. Remember the energy is typically expressed in electron volt (eV) units and the frequency is expressed in Hertz where one Hz equals 1/sec. Therefore the relation between velocity, frequency and wavelength can be written as follows;

Velocity of Light = (wavelength) x (frequency)(meters) x (cycles per second or Hertz)
= (3 x 108 m/sec)

Initial Velocity

The first question that arises when we read about distance, speed and velocity is the basic difference between speed and velocity. Velocity is the directional quantity while speed is not. We have already discussed about the importance of direction while calculating vector quantities.Having problem with Formula for Velocity keep reading my upcoming posts, i will try to help you.

Velocity in simple terms can be defined as the distance covered per unit time in a particular direction. This means that here we are also taking the direction in consideration. If we were to define speed we could have said it the distance per unit time. We will not have mentioned the direction bit.

We can divide the velocity into two parts. These are final and the initial velocity. As it is clear from the name the In. velocity is basically the starting velocity of an object or a body while final velocity is the finishing velocity. It may seem confusing at first but is quite easy.


Let us take an example. If the car starts and attains a velocity of 30 kilometers per hour then the initial vel. Considered would be zero km per hour while the final velocity will be 30 km per hour after 4 hours in a particular direction say southwards. Calculate Initial Velocity is easy. We can directly use the equation of motion which says
v = u + a t - - - - - - -(1)
Here v is the final velocity
U is the initial velocity
A is the acceleration
And t is the time taken to attain the final velocity.
Also s = u t + ½ a t 2 - - - - - - - - -(2)
Here s is the distance covered in a particular time interval.
This is the Equation for Initial Velocity. There is yet another equation for its Calculating Initial Velocity. It is:
V2 = u2 + 2 a s - - - - - - - - - - -(3)
Let us assume a ball is rolling on a platform. It attains a velocity of 10 m per seconds with an acceleration of 4 m per second 2. The time taken is 2 seconds.
Let us try to calculate the initial velocity.  Take the first equation into consideration.
So v = u + a t
10 = u + 2 * 4
10 = u + 8
u = 2
So initial vel. is  2 metre per second.
You can also calculate it according to different values of s, a, v, t in different situations.

Velocity Mass Equation

Mass in special relativity

The term mass  in special relativity usually refers to the rest mass of the object, which is the Newtonian mass as measured by an observer moving along with the object. The invariant mass is another name for the rest mass of single particles. The more general invariant mass (calculated with a more complicated formula) loosely corresponds to the "rest mass" of a "system." Thus, invariant mass is a natural unit of mass used for systems which are being viewed from their center of momentum frame, as when any closed system (for example a bottle of hot gas) is weighed, which requires that the measurement be taken in the center of momentum frame where the system has no net momentum. Under such circumstances the invariant mass is equal to the relativistic mass (discussed below), which is the total energy of the system divided by c (the speed of light) squared. I like to share this Formula for Acceleration due to Gravity with you all through my article.

The concept of invariant mass does not require bound systems of particles, however. As such, it may also be applied to systems of unbound particles in high-speed relative motion. Because of this, it is often employed in particle physics for systems which consist of widely separated high-energy particles. If such systems were derived from a single particle, then the calculation of the invariant mass of such systems, which is a never-changing quantity, will provide the rest mass of the parent particle (because it is conserved over time).
Despite the convenience that the invariant mass is the same as the total energy of the system (divided by c2) in the center of momentum frame, the invariant mass of systems (like the rest mass of single particles) is also the same quantity in all inertial frames. Thus, it cannot be destroyed, and is conserved, so long as the system is closed. (In this case, "closure" implies that an idealized boundary is drawn around the system, and no mass/energy is allowed across it).


The term relativistic mass is also sometimes used. This is the sum total quantity of energy in a body or system (divided by c2). As seen from the center of momentum frame, the relativistic mass is also the invariant mass, as discussed above (just as the relativistic energy of a single particle is the same as its rest energy, when seen from its rest frame). For other frames, the relativistic mass (of a body or system of bodies) includes a contribution from the "net" kinetic energy of the body (the kinetic energy of the center of mass of the body), and is larger the faster the body moves. Thus, unlike the invariant mass, the relativistic mass depends on the observer's frame of reference. However, for given single frames of reference and for closed systems, the relativistic mass is also a conserved quantity.Although some authors present relativistic mass as a fundamental concept of the theory, it has been argued that this is wrong as the fundamentals of the theory relate to space-time. There is disagreement over whether the concept is pedagogically useful. The notion of mass as a property of an object from Newtonian mechanics does not bear a precise relationship to the concept in relativity.

For a discussion of mass in general relativity, see mass in general relativity. For a general discussion including mass in Newtonian mechanics, see the article on mass.

Used Laser Cutting Machine

Introduction to used laser cutting machines:

First we will discuss about LASER. LASER means the Light Amplification by Stimulated Radiation and Emission. The laser beams are highly energetic and highly coherent. There are different types of laser machines, which produces laser beams such as ruby laser, helium neon laser. There are different stages of  lasers. For example, ruby laser is the three stage laser and Helium neon is a four stage laser. Let us discuss about the used laser cutting machines. Please express your views of this topic Emp Bomb Effects by commenting on blog.



Use of laser cutting machines


The laser machines cut the materials by vaporizing the material at that particular place. The laser beam is focussed on the path of the size of thick human hair. In other words we can say that the laser beams be focussed on 0.005 inch and leaving vapours and ash to exhaust. We can cut the steel sheet in a desired shape by the use of laser cutting machines.

The laser beams can cut the diamond with the very fine cut. The cutting of the diamond in the fine mode is possible due to the laser cutting machines.


Factors relating to laser cutting machines


There are some factors in the laser cutting machines. The main factors are power of the laser beams, laser focusing, speed of cut, thickness of the material which is to be cut, etc. The power of the laser cutting machine is the main factor of the machine. If the power is more, then we cut deep inside the surface and more quicker. The laser cutting machine is of 50 Watt power. We can use the power ranging between 1% to 100%. Laser machine has more power as they starts up. So we have to keep warming the laser machines. The lasers have the working area of 12 inches by 24 inches. Is this topic Physics Projectile Motion Problems hard for you? Watch out for my coming posts.


Modes of cutting through a laser


The laser cutting machine has two modes of the cutting, one is called the vector mode and the other is called the raster mode. The mode which is used for designing in the cutting is called the vector mode. Rastering mode is used for the engraving purposes. The laser head of the laser cutting machines moves back and forth to cut a picture.


Conclusion for the laser cutting machines


Laser beam should be perfectly focused before use on any material. Generally the lens of the laser cutting machines has two inches focusing length. The lenses may be shorter or longer. Longer the lenses, lesser is the accuracy. It is used to cut the wood, paper, fibre glass, diamonds, etc.

Universe Infinite Finite

Introduction to universe infinite finite:

Before the study of this topic, the first question arises that what is universe. The space in which the galaxies, black holes, solar systems, suns, moons and millions of others celestial bodies is called universe. Ancient philosophers believed that earth is the centre of the universe, around which everything else in the universe revolved. They even thought that the earth to be flat in shape. To understand the creation of the universe, we had to first learn a lot about the earth and the solar system, galaxies and so on. Here we discuss how the universe is expanding. I like to share this Electromagnetic Pulse Effects with you all through my article.


Modern theories on Universe


There are several modern theories about the beginning of the universe and its future. Now the scientists think that the big bang theory offers the best explanation about the universe. This theory was proposed when the scientists concluded that the universe is expanding. In 1920, Professor Edwin Hubble observed that the frequency of light coming from far off galaxies decreased, i.e., the frequency of the light coming from the far off galaxies showed a red shift. Professor Edwin Hubble studied these red shifts carefully and concluded as follows:

All galaxies are moving away from each other.
The speed with which any two galaxies move away from each other is directly proportional to the distance between them. This is called the Hubble’s law. The larger the distance between two galaxies, faster they move away from each other.
In other words, from the observed red shift, the frequency of light coming from the far off galaxies, Professor Edwin Hubble concluded that the universe is expanding. Thus, the universe is infinite in size.


Conclusion on universe whether it is infinite or finite


The future of the universe is totally depending on the mass of the universe. If the mass is large enough, gravitational attraction will slow down the expansion and eventually stop it. After that, the galaxies will move towards each other due to the gravitational force between them. They will merge in the one lump of the super dense material. Again, a big bang will take place and a new universe will be created. Therefore, we will have an oscillating universe.

Properties of Matter Solid

Introduction to Properties of Matter Solid:
Let us see about the properties of matter solid. Matter is prepared by molecules and atoms.  We have three states of matter. The three state of matter is differing from each other because of the difference in the magnitude in the intermolecular forces. One of the states is Solid. The solid has an exact shape and size.

Solids possess a definite shape and volume at ordinary temperature. Depending on the arrangement of atoms the properties of solid varies. Based on their internal structure, solids matter are classified into two types- crystalline and amorphous.


Types of Solids:


Based on their internal structure, solids matter are classified into two types. They are,

Crystalline
Amorphous


Crystalline Solid:

The properties are, atoms are arranged in a regular, repeated and periodic pattern in crystalline solids. This orderly arrangement of atoms resembles that of brick laying by masons. Examples of crystalline solids are diamonds, quartz, rocksalt, mica, sugar, metals, etc.

Amorphous solid:

The properties are, atoms are set in a disorderly manner in amorphous solid. The best case of an amorphous solid is glass. Other examples are plastic materials, wood, etc.


Elasticity:

An external force ‘F’ is applied on the body of mass ‘m’, the body acquire an acceleration ‘a’ such that a=F/m. Due to the change, the body may suffer a deformation. This external force is known as deforming force.

As the body is deformed, internal forces are set up within the body, which tends to bring the body back to the original shape. The force developed within the body on account of relative molecular displacement is called internal force or elastic force or restoring force.

Elasticity is the properties of the material of a body by virtue of which the body regains its original shape when the deforming force is removed. Few bodies, which do not show any tendency to recover their original shape after the removal of deforming force. Such bodies are called plastic bodies.

The property by virtue of which the body does not regain its original shape after the removal of the deforming force is called plasticity. The restoring force developed per unit area of the body is called as stress. Its unit is Nm-2. The strain produced in a body is defined as the ration of change in dimension to its original dimension. The maximum value of stress within which a body regains its original state is called elastic limit.

Hooke’s law states that within the elastic limit of the body, the stress is proportional to the strain produced.

Stress/ strain= a constant.

Using this formula, we get a constant is known as modulus of elasticity.

Table of Physical Constant

Introduction to physical constant:

A physical constant is one of the physical quantity which generally has a constant value for all mediums and all changes in the body or object and it is also assumed that the value of the physical constant is universally constant in nature as well as it is universally constant in time. The mathematical constant is different from the physical constant because in mathematics the constant has a fixed value but when we calculate it, then they do not undergoes any physical measurement of any object or system. I like to share this Equation for Average Speed with you all through my article.


Table of values of Physical Constants:

The table of physical constants is nothing but a table which has listed most of the physical constant which are used in study related to physics with their values and the respective units. The table of physical constant may contain the entire physical constant and a few constants depending on the requirements. The physical constants are also used with some of the prefixes. These prefixes must be used when defining the value of the physical constant in the table.
 

                                         Table showing some physical constants



Conclusion for the physical constants


Thus a table of physical constant can contain not only the constant names but it includes the symbol of physical constant and the value of the physical constant and the unit of the physical constant either it is SI or c.g.s. and last but not the least, the prefixes used with that physical constant. The physical constants can have the dimensions depending on the measurement taken by it and some of the physical constant exists in nature which does not have any dimension. That means, when the physical constant evolves in any system then there is a change that occurs in the system which is described in such a manner that the overall unit of the quantity is null.