Category: Physics Notes PPT

The electric field is the region around an electric charge where its influence can be observed. The existence of an electric field can be experienced when another charge is brought into the field. According to the incoming charge’s nature, the electric field will either attract or repel the charge. The electric field can be considered as a property of any electric charge. The electric field strength or intensity is defined by the charge and electrical force acting in the field.

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If the charge is denoted by q and the force experienced by it is denoted by F, then the direction of the Field lines is determined by both F and q.

What is The Electric Field Formula?

The Electric field formula is

E = F/q

Where E is the electric field

F (force acting on the charge)

q is the charge surrounded by its electric field.

If two charges, Q and q, are separated from each other by a distance r, then the electrical force can be defined as

F= k Qq/r2

Where F is the electrical force

Q and q are the two charges

R is the distance of separation of the two charges

K is Coulomb’s constant.

Therefore, electric field E can be defined as

E = F/q

or, E = k Qq/r2q

This is the electric field experienced by charge Q due to charge q.

Coulomb’s law defines this electric field intensity formula.

Again, if a voltage V exists across a distance r, then the electric field is defined as

E= V/r

The SI unit of an Electric field is N/c or Newton/Coulomb.

If multiple electric fields exist in a region, then all the electric fields add up vectorially, i.e., keeping the field’s direction into consideration.

The following electric field strength formula gives the resultant electric field existing in that place:

Fig. Formula of resultant electric field existing due to several electric fields existing in the same location.

Application of Electric Field

The concept of the electric field has several applications. Some of them include:

• Electroporation- electroporation is an invasive technique where electric fields are used to make pores in cell membranes to insert drugs, medicines, or genes. It is widely used in cloning processes.

• It is used to study tissue dynamics.

• The electric field is used to control different crystallization processes like nucleation, crystal growth, etc.

Conclusion

The electric field is the region surrounding a charge where its force can be experienced. The nature of the charge determines the direction of the field. Coulomb’s law describes the formula for electric fields. The electric field has several applications for research and industrial purposes.

According to physics, absorption of electromagnetic radiation is considered as a process that shows how a matter can take up a photon’s energy and then transform electromagnetic energy into internal energy of the absorber. One example of such an absorber is thermal energy. The absorption of waves never depends on the intensity of the matter. According to wave motion, absorption is considered as the transfer of energy of a wave to a matter; this happens when the wave passes through the matter.

Absorb Physics

Absorb definition physics is a phenomenon that happens when a wave comes in contact with a medium and forces the molecules of the medium to vibrate, move and change their places. Some of the energy of the wave gets reduced during this process because the vibration takes away some of the wave’s energy. As there is minimal energy present in the wave, therefore less of the energy gets reflected.

Let’s discuss one example of absorption. Black pavement can be considered as one of the examples because black pavement absorbs energy from light. The black pavement usually becomes hot instantly because it absorbs most of the light waves that reflect on it, and a little of the light waves are reflected back; thus, the pavement appears black. If you draw a white line on the black pavement, then it will reflect more because the white colour doesn’t absorb more light waves. So, the white strip drawn by you will be less hot as compared to other surfaces that are painted black.

Absorption in Laser Physics

According to researchers, the laser can get easily absorbed inside an optical substrate by using several methods which are distinct from each other. Electrons that are present in the discrete energy tend to level up the atoms that forced the optical medium to absorb radiative photons and are pushed to the semi-table, higher energy levels.

These atoms, after this phenomenon, start to fluoresce and begin to emit radiation in the form of photons through spontaneous emission when electrons start falling back to a lower energy level.

Unintentional fluorescence is the reason for loss of energy and also acts as a barrier in signal detection, which is considered detrimental in the case of laser optics applications. Most of the time, fluorescence is isotropic and tends to radiate in every direction, which makes things worse than before. The main cause of fluorescence is the impurities that are present in the substrate, for example, rare-earth ions.

For example, UV grade fused silica is a substance that can explain high transmittance in the UV and visible spectra. Still, they experience dips in transmittance, which are centred at 1.4um, 2.2um, and 2.7um due to absorption from Hydroxide ion impurities. On the other hand, IR grade fused silica is known for having a lower amount of hydroxide ions; this immediately results in greater transmission throughout the NIR spectrum.

The above explanation and example can make you understand what absorption is and how it operates using a laser. 

Absorption Spectrum Definition Physics

The absorption spectrum is defined as an electromagnetic spectrum within which a decrease in the intensity of radiation at particular wavelengths or various wavelengths characteristic of a specific absorbing substance gets manifested in the form of dark lines or bands.

An absorption spectrum generates when a light goes through a cold, dilute gas. Atoms that are present in the gas starting absorbing in different frequencies. Since the light which got re-emitted is unlikely to get emitted in the same direction as one of the absorbed photons, this phenomenon is the reason for dark lines getting created in the spectrum.

An absorption spectrum gets created from the frequencies of light that are transmitted through dark bands when energy gets absorbed with the help of electrons at the time when they are present in the ground state to reach high energy states.

This is what you will learn from the absorption spectrum. It isn’t easy, but regular practice can help you achieve perfection in this particular topic.

All solid substances have the capabilities to attract to their surfaces molecules of solutions or gases with which they are contacted is called adsorption. Here in this article, we will understand the adsorption meaning, types of adsorption like chemical adsorption, physical adsorption, isothermal adsorption. Also, we will discuss different adsorbate and adsorbent. So, let’s discuss adsorbate and adsorbent before any discussion. Well, the solids that are used to adsorb dissolved substances or gases are known as adsorbents and the molecules that are adsorbed by solids are collectively known as adsorbate. Let’s take an example of charcoal. Charcoal is an adsorbent as it removes impurities and poisons from air or stream in gas masks. 

Define Adsorption

Adsorption is the process of collecting molecules by the internal surface or external surface of solids or by liquid surface. Adsorption refers to the collecting of molecules by the external surface or internal surface (walls of capillaries or crevices) of solids or by the surface of liquids. You may have confusion with the word adsorption and absorption. Absorption is the process of penetrating the substance of blocks of amorphous liquids or solids, or into the actual interior crystals. Sometimes a solid takes up the liquid or gas without specifying a particular process of absorption or absorption, such process is called sorption.

Difference Between Adsorption and Absorption

Most people have confusion between these two terms as they sound similar but both the processes are different. Adsorption is the surface phenomenon and is an exothermic process. It depends on temperature and initially, the process will increase and will decrease gradually. Whereas, absorption is an endothermic process. Absorption is not affected by temperature and occurs at uniform rates. Substances penetrate the surface of the material. Absorption is spontaneous whereas adsorption is not spontaneous. Absorption is unique throughout the surface area and adsorption is not unique on the surface area. Molecule interaction is higher in absorption than adsorption.

Types of Adsorption

Adsorption is classified into two types further, physical adsorption and chemical adsorption. Adsorption, an exothermic process is an attractive force that takes place in-between the adsorbent and adsorbate, where heat is released. Moreover, the chemical and physical adsorption also depends upon the forces between adsorbent and adsorbate. In physical adsorption, gases get condensed to liquids depending on Van der Waals, or forces exist between adsorbates and solid absorbents. If the temperature is low and gas pressure is quite high, then solid can adsorb any gas without concerning chemical specifications. Whereas in chemical adsorption, the process depends upon the chemical forces acting upon the solid surfaces and gas absorbates. Chemical adsorption needs a higher temperature as compared to physical adsorption. Chemical adsorption involves energy activation, hence, it takes time and it is a slower process.

Physical Adsorption and Chemical Adsorption: Difference

Adsorption Isotherm

Research on environmental protection and techniques of adsorption involves adsorption isotherm as it helps in the prediction of the adsorption capacity of the solid material. Furthermore, an adsorption isotherm is a graph that represents the amount of adsorbed adsorbate on the adsorbent surface keeping a constant temperature and changing pressure.

Application of Adsorption

Charcoal adsorbs the colouring molecules from the coloured sugar solution and decolorizes it.

Moisture is adsorbed by silica gel from the desiccators Alumina and silica gels remove moisture and control the humidity of offices and rooms because they act as adsorbents. In gas masks, activated charcoal is used as it adsorbs vapours, toxic gases to purify the breathing air. Heterogeneous catalysis is carried out through the adsorption process. Charcoal can be used as an absorbent to separate noble gases. The chromatographic analysis is based on the adsorption phenomenon. In syrups and cosmetics, stable emulsions are formed through adsorption. Drug adsorption kills germs.

Sound and music are intricately linked with our everyday lives. We can perceive different sounds due to the elaborate human ear anatomy and specific characteristics of the sound itself (such as pitch and frequency). The external ear consisting of the pinna, the auditory canal, and the tympanic membrane, the ossicles of the middle ear, and the inner ear comprising of the cochlea, the semicircular canals, and the vestibule constitute the structure of the human ear. So, let us learn about the nature of sound waves and how the anatomy of the human ear enables the detection of sound. 

Nature of Sound Waves

• Sound waves as mechanical waves: Sound is a disturbance that is transmitted through a medium via particle-to-particle interaction. Hence, sound waves are mechanical.

• Sound waves as longitudinal waves: Sound waves are longitudinal, meaning that the direction of propagating sound waves is the same as the vibration of the medium particles.

• Sound waves as pressure waves: The vibrating particles of the medium interact with the air particles. Hence, there are regions of high pressure (compressions) and areas of low pressure (rarefactions). 

Frequency, Pitch, and Human Perception of Sound

Frequency: It indicates the rate of vibration of medium particles when a wave passes through it. Its unit is Hertz, where 1 Hertz = 1 vibration/second.

Pitch: It is the sensation of frequency. High pitch corresponds to high-frequency sounds, whereas low pitch relates to sounds of low frequency.

The human ear is capable of perceiving sound waves ranging between 20 Hz to 20,000 Hz. 

Anatomy of The Human Ear

The human ear performs the functions of perception and interpretation of sound waves. The ear is divided into three parts:

• External ear

• Middle ear

• Inner ear 

The External Ear

The external ear consists of the following parts:

Pinna: It is a flap of cartilage located on the side of the head. Its peculiar shape, made up of thick folded cartilage, is well-suited for gathering the sound waves and directing them towards the auditory canal.

Auditory Canal: It is an inch long tunnel that ends at the tympanic membrane or the eardrum. The channel contains hairs and glands for secreting earwax.

Tympanic Membrane: It is a thin membrane, stretched tight like a drum head, located between the middle and the outer ear. When sound waves strike the membrane, it vibrates to produce sound.

The Middle Ear

The middle ear is an air-filled hollow cavity and is separated from the outer ear by the tympanum. The middle ear’s anterior wall contains an opening that leads directly into the Eustachian tube; this tube connects the middle ear to the throat and equalizes the air pressure on either side of the eardrum.

Ear ossicles: The air space of the middle ear has an arch of three small bones – the malleus, the incus, and the stapes. These three bones are collectively termed as ear ossicles. The vibrating eardrum transmits the vibration to the ear ossicles, which relay the vibration to the inner ear.

The Inner Ear

The inner ear or the labyrinth is composed of the cochlea, the semicircular canals, and the vestibule. The bony labyrinth is filled with a fluid called the perilymph.

Cochlea: It is a bony canal with two-and-a-half spirals connected to the middle ear via the oval window. The cochlea is internally separated by membranes into three canals. The upper canal and the lower canal are filled with perilymph, while the central canal has endolymph.

The central canal also possesses sound receptors called organs of Corti; its hair cells transform sound vibrations to nerve impulses and are suited for the interpretation of sounds of different frequencies.

Semicircular canals: It is a set of three fluid-filled channels arranged perpendicular to each other and are responsible for the maintenance of body balance in motion.

Vestibule: The central portion of the labyrinth consists of two sacs – the utricle and the saccule. The vestibule has receptors for the maintenance of the body’s static equilibrium.

Diagram Showing The Internal Structure of The Human Ear

Given below is a simple human ear diagram for class 9:

In 1973, during a special two-week sequence of synopsis commemorating Copernicus’ 500th birthday, the Anthropic Principle was proposed in Poland. It was suggested by Brandon Carter, who had the audacity to declare on Copernicus’ birthday that humans did indeed occupy a peculiar position in the Universe, a statement that is diametrically opposed to Copernicus’ almost widely acknowledged idea.

Carter, on the other hand, was not saying that the Universe was our own sandbox, created with mankind in mind. Our entire behaviour as carbon-based intelligent beings imposes a sort of selection effect on the Universe, according to the variant of the Anthropic Principle he suggested that day, now known as the Weak Anthropic Principle (WAP). Carter suggested the Strong Anthropic Principle, which states that the universe had to bring humanity into being. 

The Following is the official Anthropic Definition:

The anthropic principle definition is the belief that scientists may use human life as a starting point to infer predicted properties of the universe that are compatible with the creation of human life if we consider human life as a given state of the universe. The anthropic principle is a theory that’s essential in cosmology, particularly when it comes to dealing with the universe’s apparent fine-tuning. In short, the anthropic meaning is the cosmological principle that theories of the universe are reserved by the necessity to allow anthropist (human existence on earth).

The anthropic principle theory is expressed in a variety of ways. Based on the kinds of cosmological statements involved, the anthropic principle can be divided into “weak” and “solid” categories.

Weak Anthropic Principle (WAP)

Brandon Carter describes the weak anthropic hypothesis, which argues that the universe’ ostensible fine-tuning is the result of selection bias. Both physical and cosmological quantities have found values that are not equally likely. However, they are constrained by the requirements that there be places where carbon-based life will evolve and that the Universe be ancient enough for it to have done so already.

Moreover, for there to be a statistical population of the Universe to choose from, such claims depend on some notion of the multiverse. However, a single vast Universe is sufficient for most forms of the weak anthropic principle that does not specifically deal with fine-tuning.

Strong Anthropic Principle (SAP)

Carter proposed the Strong Anthropic Principle, which states that the Universe had to bring humanity into being. This version is a lot more teleological, but not theological, and it’s a lot more speculative in nature. At some point in its evolution, the Universe must have properties that cause life to evolve within it. 

In addition, the weak anthropic principle and the strong anthropic principle, there are the Participatory and Final Anthropic Principles. The Participatory Anthropic Principle states not only that the Universe had to develop humanity but that we are necessary to its existence (anthtopist), as it takes an intelligent observer to collapse the waves and possibilities of the Universe from superposition into a more realistic truth. According to the Final Anthropic Principle, after the Universe has produced knowledge, it will never die out. 

Applications of Anthropic Principles

The Nucleosynthesis of Carbon-12

Anthropic inference may have been used by Fred Hoyle to forecast an astronomical event. He said to have reasoned, from the prevalence on Earth of life forms (anthropist) whose chemistry was based on carbon-12 nuclei, that there must be an undiscovered resonance in the carbon-12 nucleus facilitating its synthesis in stellar interiors via the triple-alpha process. Also intended the energy of this undiscovered resonance to be 7.6 million electronvolts. Willie Fowler’s team discovered the resonance quickly, and the measured energy was similar to Hoyle’s estimate. 

Cosmic Inflation

Initial conditions for a thermodynamic arrow of time in a universe with a Big Bang origin would require the presumption that the universe’s entropy was strong at the initial singularity, making a thermodynamic arrow of time extremely unlikely. In response to this critique, Paul Davies invoked an inflationary version of the anthropic principle. Paul Davies accepted the premise that the initial conditions of the visible universe had to possess a very low entropy value due to random quantum fluctuations to account for the thermodynamic arrow of time that has been observed, he deemed this fact an advantage for the theory. Since the tiny patch of space from which our visible universe grew had to be incredibly orderly in order for the post-inflation universe to have an arrow in time, hypotheses about the original entropy state are needed, as are hypotheses required by other Big Bang theories.

String Theory

String theory predicts a large number of the possible universe, this is called the “backgrounds” or “vacua”. The set of these backgrounds is often called the “multiverse” or “anthropic landscape” or “string landscape”. According to Leonard Susskind, the presence of a vast number of vacua grounds anthropic logic. Only universes with properties that allow observers to exist are observed, while a potentially much greater number of universes with properties that do not allow observers to exist go unnoticed. Steven Weinberg believes the Anthropic theory may be appropriated by cosmologists committed to nontheism and considers the application of the Principle to the string landscape to be a “turning point” in contemporary science.

The Relation Between Atmospheric Pressure and Gauge Pressure

Pressure, the measure of force in a given area, is a simple concept. However, depending on the query, there can be several different ways of understanding the strain. Here are several guidelines that will help distinguish forms and units of pressure measurement when explaining when and why such pressure measurements are being used.

 

What is Gauge Pressure?

The gauge pressure is the pressure measured relative to the ambient atmospheric pressure. The gauge pressure can be measured using a diaphragm sensor, where one side of the diaphragm is exposed to the pressure media to be measured, while the other side is exposed to ambient atmospheric pressure.

When measuring the gage pressure, it should be noted that the measured gage pressure changes with changes in barometric pressure due to changes in weather patterns, unless the measurement point is itself exposed to ambient atmospheric pressure. Sensor for calculating the pressure gage In vacuum systems, measuring and monitoring the pressure gage may be used to accurately ventilate the vacuum chamber to ambient pressure and avoid contamination of the particles when opening up to the atmosphere. This practice is also used in semiconductor load lock applications.

 

Different Types of Pressure

There are several ways in which pressure can be referenced. The application must be considered in order to accurately identify and relay pressure measurements. Pressure sensors shall use the following references – 

Gauge Pressure uses a reference to the atmosphere around the sensor. Since the sensing device has a deflection due to a change in pressure, a reference point is required to determine exactly what pressure is being measured. Pressure sensors that use gauge pressure — usually seen in PSIG, BARG, and kPaG — have some kind of vent. This vent can be installed in the sensor or even in the electrical connection by means of a tube. The vent is positioned to use atmospheric pressure as a reference point for the media measurement sensor. One common reason for the use of gauge pressure is to ensure that, with any location in the world, the sensor will always refer to the location at which it is installed.

Absolute Pressure as its reference to the perfect vacuum. This type of pressure reference is the pressure gage of the media plus the pressure of the atmosphere. As locations change, particularly when managing elevation changes, the reference point can change due to variations in atmospheric pressure. The use of an absolute pressure sensor removes the relation to changing atmospheric pressure and relies on a common reference pressure range.

Differential Pressure can be a little more complex than the gage or the absolute, but it basically measures the difference between the two sources. While most gage pressures are theoretically a differential pressure sensor — measuring the difference between the media and the ambient pressure — a true differential pressure sensor is used to measure the difference between the two distinct physical areas. For example, the differential pressure is used to regulate the decrease or loss of pressure from one side of the body to the other.

Sealed Pressure is less popular than the previous three, but it still has a place in the pressure world. Sealed pressure uses a default reference point, not just a vacuum. It makes it possible to measure pressure in areas that can vary based on atmospheric changes. According to the predetermined reference point, no ventilation of the sensor is necessary.

 

Units of Pressure

Many units are widely used when measuring strain. Some of these units of measurement can be used for the universal unit system, such as kilo, mega, etc. These units shall be defined as follows:- 

PSI (Pounds Per Square Inch): is the unit of measure for one pound of force applied to one square inch of area. PSI is a typical pressure unit in the United States. 

BAR: One bar is equivalent to Earth’s air pressure at sea level. The BAR device has been developed in Europe and is still widely used there.

PA (Pascal): One Pascal is equal to one Newton of pressure per square meter. 

InHg (Inches of Mercury): that’s the pressure exerted by a one-inch circular column of mercury, one-inch thick, at gravity, and by 0 ° C (32 ° F). Usually, barometric pressure is used inHg.

Torr: This is the pressure exerted by a one-millimeter-high circle column of mercury. It was also known to have a millimeter of mercury (mmHG). It’s equal to 1/760 atmospheres. 

InH₂O (Inches of Water): this is the unit of measurement for a one inch circular column of water, one inch wide, at gravity, and 4 ° C (39.2 ° F). It is typically used for differential pressure measurements or for low-pressure water applications.

Absolute pressure is defined in many applications without any specific need for it. There is a misunderstanding that all pressure measurements must be absolute. Although absolute pressure measurement is definitely required, most applications require only a gage pressure or an alternative. By knowing the application specifics, it can be simple to pick an acceptable pressure sensor. The correct pressure sensor allows for more precise processes and the most efficient and economical performance.