Category: Physics Notes PPT

Many materials possess a tremendous property to hold their electrical charge for long intervals and in large quantities as well. Such property of materials refers to dielectric property. Many students get confused with the term dielectric constant, property, and often ask what is relative permittivity. This guide is beneficial to understand the meaning and factors affecting the dielectric constant. 

 

What are Dielectric Materials?

Dielectric materials have weak electrical conductivity but possess the ability to store an electrical charge. There are several dielectric materials, including vacuum, air, and more. The values of dielectric constants of some dielectric materials include:

• For air- 1.00059

• For glass- 3.8-14.5

• For paper- 3.6

• For vacuum- 1.00

• For PVC- 4.0 

 

What Is Meant By Dielectric Constant?

The dielectric constant of any substance refers to the relative permittivity of the dielectric substance. It is the proportion of the permittivity of the material to the permittivity of the free space. Mathematically, the dielectric constant can be expressed as:

 

K = [frac{epsilon }{epsilon_{0} }]

 

where K refers to Dielectric constant

             [epsilon] refers to the permittivity of the substance

             [epsilon_{0}] is defined as the permittivity of the free space

 

Dielectric Constant Theory

Many students ask what the meaning of dielectric constant is. In order to understand the meaning of dielectric constant, it’s crucial to first understand the theory behind it. Dielectric constant serves as the major factor required to describe a capacitor. A capacitor is an electronic device built by inserting a dielectric insulating plate in-between the metal conducting plates. It’s the layer made from a dielectric material that decides if a capacitor can store a high charge or not. That’s why it is essential to choose the best dielectric material depending on the dielectric property. 

 

From the dielectric constant formula:

 

K = [frac{epsilon }{epsilon_{0} }], we get the value of relative permittivity of free space is always greater than or equal to relative permittivity of substance. Hence, the value of the dielectric constant (K) is always either equal to greater than 1. 

 

What does a High Dielectric Constant Mean?

The high value of the dielectric constant means the value of capacitance can be maximised. It can be seen from the capacitance formula in the parallel plate capacitor:

 

C = Kϵ0 A/d

 

where K refers to the dielectric constant

 

C refers to the capacitance of a parallel plate capacitor.

 

A refers to the area of parallel conducting plates

 

[epsilon_{0}] is defined as permittivity of free space

d refers to the separation between parallel conducting plates

 

Hence, from this formula, it’s clear that there are two ways to increase the value of capacitance. The first is to decrease the separation between parallel conducting plates, and the second is to enhance the dielectric constant value. 

 

What Do You Mean by Dielectric Constant Equation?

According to the dielectric constant equation:

 

K = [frac{epsilon }{epsilon_{0} }]

 

K is the ratio of two entities with the same dimension. Hence, the dielectric constant is a unitless and dimensionless quantity. 

 

What Factors Affect the Value of the Dielectric Constant?

After knowing what is dielectric constant, there come different factors that affect the dielectric constant value such as:

• Temperature: The arrangement of molecules in the dielectric material is tough at the low temperature. However, with the increase in temperature, the dipole moment increases, and hence there is a rise in the dielectric constant value. The temperature at which the dielectric constant starts increasing refers to the transition temperature. Moreover, if the temperature goes above the transition temperature, the dielectric constant will start decreasing. 

• Heating Effect: The students asking what is dielectric property can understand from the fact that on heating any dielectric material, there is a dielectric loss. It is due to the dielectric property of the material due to which whenever there is any movement of molecules inside the material, there is the dissipation of energy. When the dielectric material absorbs electrical energy, it dissipates energy in the form of heat.

• Applied Voltage: The value of the dielectric constant decreases in the presence of a direct current voltage. However, the dielectric constant value increases when an alternating current voltage is applied. 

• Frequency: The frequency of the applied voltage serves as one of the critical factors that affect the dielectric constant to a great extent. Whenever there is an increase in the frequency of the external voltage applied, the dielectric constant value becomes non-linear. 

• Humidity and Moisture: When there is an increase in humidity or moisture, there is a decrease in the strength of dielectric material. 

 

The Coulomb force present between the two-point charges in a material is affected by material property; this process is termed as relative permittivity of a material. The factor relative permittivity is used to decrease the charges present between the electric field relative to the vacuum.

While comparing the relative permittivity of two similar capacitors, the relative permittivity can be easily defined as the ratio between the capacitance of the capacitor of a material to the capacitance of that of a vacuum. 

Relative permittivity is widely known as dielectric constant also.

The historic name for the relative permittivity is the dielectric constant. Because of its ambiguity, some older records used it widely as absolute permittivity instead of the term dielectric constant. This term is deprecated by the standard organizations. The permittivity is considered as either a static property or a frequency-dependent variant.

Applications

Relative permittivity has a huge number of applications too. Some of the major applications which are common are described in detail below:

Energy:

Relative permittivity in the case of energy is used as an essential piece of information that is further used in designing Capacitors. The following material might be expected to introduce capacitance into a circuit. The materials which are having high relative permittivity when placed in an electric field reduces the magnitude of that particular field within the volume of the dielectric. The following process which is described above is used to increase the capacitance of a capacitor design. In printed circuit boards (PCBs) there exists a layer beneath the attached conductor’s which act as a dielectric.

Communication:

These are majorly used in RF transmission lines. Polyethene is highly used in between the centre conductor and outside shield, in the case of a coaxial cable. When placed inside waveguides which are also used to form filters. The best example of dielectric waveguides is optical fibres. This waveguide consists of doped impurities which further helps in order to control the precise value of relative permittivity within the cross-sections. Being an appropriate factor to control the refractive index of the material, these are highly used in optical modes of transmission. However, technically the relative permittivity matters because they are not operated in the electrostatic limit while considering the above-mentioned case.

Environment:

Relative permittivity plays a vital role in changes in environmental factors. The air is highly affected by the changes in temperature, humidity and barometric pressure. Due to the changes in the relative permittivity, changes in the capacitance occur. These changes can be measured through sensors. As barometric pressure is always fairly stable, most of the changes occurring in the environment are due to the effect of temperature and humidity only. 

Taking into consideration capacitance and the measured temperature along with using the engineering formulas the relative humidity can be obtained.

Chemistry:

The measure of the chemical polarity is the relative static permittivity of a solvent. In
order to understand the above statement let us consider an example. As we all know that water is highly polar in nature the relative static permittivity of water is 18.10 at 20⁰C. On the other hand, n-hexane is a nonpolar solvent with a relative permittivity of 1.89 at 20⁰C.  While dealing with analytical chemistry, this information is highly used in order to design separation, sample preparation and chromatography.

These are some of the major applications highly used on the basis of dielectric constant.

As a kid, we all had this dream of going to space and exploring the unknown. Watching the series on Discovery about space and planets always makes us awestruck. The feeling of being weightless and flying in zero gravity is still something we use to dream in the night. One of the things about space is it is filled with massive objects that are a part of an enormous ballad dancing act. Planets, stars, galaxies all are moving at such a high speed, but none of them are hitting each other. That’s how beautiful space is. From space, we have two things which are not a very common site to humans, the first one is the comet, and then we have asteroids. Both of these are giant rocks that are moving in space with high speed. Still, there are several differences between them, and we are going to discuss these differences between asteroid and comet today in this article. 

What Is Asteroid?

Before we talk about comet vs asteroid, we need to define what does an asteroid means and its proper definition. Asteroids are small and large formations of the rock that orbit the massive bodies in space, such as the sun. They revolve around stars just like planets, but they are quite small in comparison to planets. If you look at our solar system, you will find there are quite a lot of asteroids present in our system. 

Most of the asteroids that we are present in our system resides in the asteroid belt, a region between the orbits of Mars and Jupiter. But don’t think about that’s the only place where you could find an Asteroid, they hang around in other places as well. For example, some asteroids can be seen orbiting the sun on the same path of a planet. Meaning both the planet and the asteroid are following the same way of moving around the sun. Earth is one of the planets that have asteroids like this in its sun’s orbit. 

(Asteroid on its way to hit the earth, the depiction is fiction based, please don’t consider it to be a real image.)

When talking about asteroids, we need to describe how they formed in the first place. The early signs of our solar system came around 4.6 billion years ago when the big cloud of gas and dust started to collapse inwards. When this was happening, most of the dust particles and dense gases reached the centre of the cloud and formed a star, which we now see as a sun in the day time. 

Other particles that are left behind formed planets in the coming years and those who are left behind were made into small rocks in space, which is called asteroids. 

What Is A Comet? 

In winter, when it is cold you have snow outside, in the same way, space is insanely cold, and thus, some gases come together and form a dusty snowball called comets. These space bodies also orbit around the sun, and they are made up of ice and water for most of the part along with carbon dioxide, ammonia, and methane. 

The centre of the comet is made from ice, and it is covered with a large cloud of gas and dust. It is said that comets are the ones that brought water and other organic compounds that worked as building blocks of life on our earth. 

There’s a special belt of comets in our solar system, which is called the Oort cloud. Comets present in this orbit can take up to 30 million years to complete their single rotation around the sun. Oort cloud has a distance 100,000 times more than the distance between earth and sun.

(A comet going it way in space, which is close to the earth.)

Every comet has a nucleus in the centre, which is smaller than a few kilometres across the length. As we said it the earlier nucleus of a comet is made from the big icy rocks, frozen gases, and it does have some dust particles also. This sum up all your doubts about what is a comet.

Now, we talk about the tail of the comet, which we make so unique in the night sky. When the comet comes near to earth, it also comes close to the sun. As a result, it starts to develop the atmosphere around itself, as gases and the water begins to melt on the surface. The pressure from the sunlight causes the atmosphere, thus, forming a long bright tail. There are two tails of a single comet, one is the dust tail, and the other one is ion tail, which develops due to gases present inside the comet. These are some of your difference between comet vs asteroid for your better understanding. 

Force and pressure are the two basic concepts of Physics which are usually wrongly misinterpreted by people. Force and pressure are different entities, and there are vast differences between them, which you can understand only if you have thorough knowledge. Have you ever thought about how football moves? Or how a drawer opens? This happens when the force is applied to an object. In simple words, force is the pull or push which changes the state of motion or the state of rest or the direction of an object.

Have you ever thought why the tools which are used to cut, trim, chop or pierce items have sharp edges? Have you wondered why heavy vehicles have broad tyres? Here comes the concept of pressure, which is the applied force per unit area. This article provides you with some simple and significant differences between force and pressure.

Definition of Force

Force is the push or pull, which arises due to the physical interaction of two objects, and which changes or tends to change the present state of the object. Force is a vector quantity, i.e. it has both magnitude and direction. The magnitude of force determines the amount of force applied to an object.

In simple words, force is the influence which changes or tends to change the state of motion or rest of the body upon which it is applied. The speed and direction describes the state of the motion. When force is applied to an object, it can change its state of motion or its shape.

 

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When more than one force is applied to an object, the resultant force is called a net Force. When two different forces are subjected to an object in the same direction, then the resultant force is the sum of two forces. And when two different forces are applied in the opposite direction, the resultant force is the difference of the applied forces.

Broadly, the Forces are of Various Types, These are:

• Contact Force

• Muscular Force

• Frictional Force

• Non-contact Force

• Magnetic Force

• Electrostatic Force

• Gravitational Force

Definition of Pressure

The amount of force applied per unit area of a surface is called pressure. In simple words, it is the force acting perpendicularly over the surface of the area, which makes it spread about that area. When force is applied to a large surface area, the pressure is low, and when force is applied to a small area, the pressure is high.

 

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The pressure is the forces spread out by continuous pressing or pushing of two objects with each other. It is calculated as follows:

Pressure = Force / Area

Or, Mathematically: P = F/A

Where:

P is the pressure,

F is the magnitude of the external force, and

A is the surface area of the surface in contact.

Unlike force, the pressure is a scalar quantity, and it has only magnitude. The vector of force acting normal to the surface is the vector element of pressure.

Importance of force and pressure 

The impact of one object over another is Force and the physical quantity of force that is spread over a particular area is Pressure. Force can be defined as a push or a pull that makes an object, or a thing change its state of direction or motion. A force is always applied to a ball when we want to hit the ball, and until the ball is stopped by a motion of gravity, or by friction, the ball will be in motion.

A force can stop a moving object or body, it can make it move faster and it can even make the object or the body change its direction. Force has magnitude and direction.

The physical quantity of force that is spread over a particular area is what we say to be Pressure. Let us take the amount of force that is being applied to an object or a body. If this is divided with the area of contact, then we will get the pressure that is applied to the object or on the body.

We can say that:  pressure=force/area,  which implies that if the same force is applied on an area that is smaller, that will produce a greater pressure compared to when applied to a larger area.  

The process of nuclear fusion is as opposed to that of nuclear fission. By considering the following scenario, we can distinguish between nuclear fission and nuclear fusion.

When two highly active atoms collide and fuse to form a larger atom due to the strong inter-atomic force of attraction, this is referred to as nuclear fusion. Similarly, when a source of energy (light) splits into quanta or photons, this is referred to as the nuclear fission process.

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What is the Distinction between Nuclear Fission and Nuclear Fusion?

Nuclear Fission

The term “fission” clearly denotes the splitting or breaking of something into smaller pieces. In this context, nuclear fission refers to the breaking or splitting of a large or parent atom into smaller ones, or two or more daughter atoms. These small atoms are technically light in their weight.

When the nuclear fission process breaks, a large amount of energy is released, indicating that the nuclear fission process is exothermic.

Nuclear Fusion

The term “fuse” refers to the joining of two or more objects. The term ‘nuclear fusion’ refers to the process by which two or more atoms combine to form a larger atom. The nuclear fusion process is endothermic because it requires absorbing energy to fuse two atoms. Consider two train bogies joining or fusing via a magnet.

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The Distinction between Nuclear Fission and Nuclear Fusion in Tabular form:

What are Nuclear Fission and Nuclear Fusion in Physics?

Atoms are held together by two fundamental natural forces: weak and strong nuclear bonds. The binding energy is the total amount of energy held within the atomic bonds. The greater the amount of binding energy held within the bonds, the more stable the atom. Furthermore, atoms attempt to become more stable by increasing their binding energy.

Nuclear Fusion versus Nuclear Fission

Nuclear fission and nuclear fusion reactions are both chain reactions, which means that one nuclear event causes at least one other nuclear reaction, and the chain reaction typically continues. As a result, an ever-increasing cycle of reactions emerges, which can quickly become uncontrollable. A nuclear reaction of this type can have multiple splits of heavy isotopes such as Uranium 235U or the combining of light isotopes such as 2H and 3H).

Only when neutrons break unstable isotopes do fission chain reactions occur. This type of impact and scatter process is difficult to control/bear, but the initial conditions are relatively easy to achieve.

The fusion chain reaction, on the other hand, develops or occurs only under extreme pressure and temperature conditions that are kept stable by the energy released during the fusion process. We also discovered that the initial conditions and stabilising fields are extremely difficult to implement with our current technology, implying that Physics requires extremely advanced technology to carry out this extreme process.

Use of Nuclear Fission and Nuclear Fusion

It is well known that the basic unit of matter such as atoms themselves consist of electrons, protons and neutrons. Neutrons and protons are present at the centre of the atom and the electrons are arranged around it in their valence shells. The number of neutrons and protons in an atom decides the chemical characteristic of the atom or the properties of the element they are identified with.

All these atomic particles are held with a strong nuclear force that acts at a very close distance. When electrons change the valence shells then the change in the energy contained in the atom is observed. When an electron transfers from outer valence shells to inner valence shells then it does so by absorption of energy. Inversely, when an electron transfers from the inner shell to the outer shell then it does so by releasing energy. By general concept, the energy released is very vast compared to other forms of energy that we use in every other activity. After the discovery of this fact, many scientists have developed the method of extracting and utilising this immense amount of energy obtained from this method.

Isotopes of an element are a form of that atom having the same number of neutrons but diff
erent numbers of protons and electrons. In these types of atoms, it is relatively easy to detach the electrons and protons along with the energy holding them. This method of obtaining energy by splitting an atom into two parts is known as Nuclear fission. Contrastingly it is when two atoms merge giving release to energy. This method of obtaining energy is called nuclear fusion. This method of releasing energy occurs in the Sun and other stars. In these luminous celestial bodies, two hydrogen atoms merge to form a helium atom.

Since our elementary schooling, the first and foremost important thing students have been taught is identifying colours. Generally, it said that there are seven unique colours. All seven colours are the constituents of the white colour. When we observe the electromagnetic spectrum it is a continuous one, though there are seven unique colours, it is mixed with the different wavelengths. Similarly, the violet colour and the purple colour correspond to the same range but the key difference is the wavelength of the two colours is different. 

Difference Between Violet and Purple

Understanding the difference between Violet and Purple is the first step in understanding the wavelength range of the colour in the visible spectrum. So, violet and purple colours are two different colours that are taught to students since the very beginning of learning. 

The important and main difference in understanding these two colours is that Violet is an actual colour that generally is noticeable in nature that is due to its presence in the electromagnetic spectrum. The range which the colour has or a wavelength we can say more accurately is that ranges from 380 nm to 450 nm.

The purple colour is an unnatural mixture of red and blue that leads to its creation. The violet colour on the other hand can be produced with the help of a prism. When white light is passed through the prism, we know that the white light will split into seven different colours (generally known as the VIBGYOR). The phenomenon of splitting white light into seven distinct wavelengths is known as dispersion. The dispersion process will be helpful in understanding the difference between violet and purple colours respectively.

Where lies the difference? Violet is a so-called spectral colour. It means that it has its own place in the visible spectrum around 380 – 420 nm and thus has its own wavelength. The colour Purple which is on the other hand is a simple combination of two spectral colours blue and red.

Our colour vision which we generally possess is based on the function that is of three different colour-sensitive cells termed cones. These cones that are activated by various wavelengths are said to be however each of the three is specific in activation. The Signals which are from the cones are subsequently processed in such a way that we see the colours that we see.

On the scheme that is below we can see the CIE 1931 colour (pigment) space which corresponds basically to the signals from activated cones after being processed by the brain. So as we can notice different wavelengths activate differently which is with the cones with various intensities. Thus what we perceive for example as red is a bit more than 700 nm which is actually the activation of only red cones. On the other hand, the colour we perceive as green 495 – 570 nm is created by the activation of both green and red cones, however, colour green ones are much more activated.

Difference between Purple and Violet Colour

In optics, the violet colour is a spectral range. The purple colour is a mixture of many single wavelengths. The colour violet is said to be closely associated with purple. Whereas if we look at the purple colour we see that it is the colour of various combinations of red and blue and slightly violet. Some of which the humans perceive as similar to violet. In common usage, we can say that both refer to colours that are between red and blue in hue along with the violets that are closer to blue and purples closer to red. In the colour, traditionally the painters use purple or violet colours and both of them are considered to be placed between red and blue along with purple which is closer to red in the spectrum range.

The human eye can see that the L red cone in the eye is primarily sensitive to long-wavelength light in the yellow-red region of the spectrum. But it is also somewhat known as the sensitive part to the shorter wavelength that is of violet colour light that primarily stimulates the S that is the blue cone. 

As a result, we can see that when violet light strikes the eye the S-cone is said to be stimulated strongly and the L-cone is stimulated weakly. Accordingly, in this article, we have discussed that strong blue light mixed with weaker red light can mimic this pattern of stimulation in the result which is causing humans to perceive colours that have the same nature as violet, but the major difference is here with lower saturation. Television screens and Computer screens rely on this phenomenon. Because they use the model of the RGB colour. They actually cannot produce light that is violet and instead substitute purple that is combining blue light at high intensity with the red light that is of approximately half the intensity.

The earliest pigment is of the violet used by humans that are found in prehistoric cave paintings. 

Again notice that they were made from the minerals manganese and hematite. The term that is Manganese is still used today by the Aranda people and said to be a group that is of indigenous Australians as a traditional pigment that is for colouring the skin during rituals. It is also said that these things are used by the Hopi Indians of Arizona to colour ritual objects.

Famous Colours in the Ancient World

The most famous of all the colours that are a violet-purple dye in the ancient world was Tyrian purple. This was made from a type of sea snail known as the murex which was later found around the Mediterranean. In western Polynesia, we can see that the residents of the islands made a violet dye that was similar to Tyrian purple from the sea urchin. In Central America also we could notice that the inhabitants made a dye from a different sea snail and then the purpura which was found on the coasts of Costa Rica and Nicaragua. 

The Mayans generally used this pigment to dye fabric for religious ceremonies and the Aztecs used it for paintings of ideograms where it symbolized royalty.

Now, let us have a look at a few remarkable and important differences between purple and violet colour:

Difference Between Violet and Purple Colour

These are the important differences between violet and purple colors that can be noticed by anyone. Physics is the subject of nature and enables us to enhance the beauty of nature by understanding what is happening around us.

Did You Know?

1. Carrots used to be Purple in Colour, Now Most are Orange.

When we look for the fun facts of the colour purple, the first one noticed will be purple carrot theories. There are many theories (also stories) as to how and why most carrots are now orange. As far as we can tell, Dutch history has something to do with it. As the story suggests, 17th-century Dutch farmers started to cross-breed specifically for orange carrots in honour of their ruler, William of Orange.

2. Porphyrophobia is Fear of the Colour Purple.

This sounds strange but yes, there are people who are scared of the colour purple. We can’t imagine someone being frightened of the colour purple, however, fearing purple colour is a real thing!“ The fear of virtually any colour or the pigment is linked to negative associations. The fear can develop as a result of observation or personal events and experiences, but it often goes back to either a conscious or subconscious mindset, but the extremely negative association between the colour purple and something that left a lasting negative and scary impression.”

3. Purple Day is Celebrated on March 26.

Purple Day was founded in the year 2008, by Cassidy Megan of Nova Scotia, Canada. Purple Day is celebrated on March 26 and was celebrated to raise awareness for epilepsy.

4. Violet, or Purple, Eyes are Extremely Rare.

We might have seen celebrities with violet or purple eyes. Most of those people are wearing purple contact lenses – to be noticed and look at different individuals and to be remembered. Violet eyes are very rare, only a few people with Albinism or Alexandria’s Genesis may have that colour eyes. 

Conclusion

Understanding the difference between violet and purple at the student level is very vital that will help in the long term.

Microscopes are present in varying particular usage. The most common types of microscopes are the light and the electron microscope. Each of these microscopes bear distinguishing features and is suitable for different purposes. Also, both light and electron microscopes use radiation to form complete images of objects that a human eye cannot view. 

The key difference between light and electron microscope is that a beam of electrons is employed for magnifying the image of an object while visible light is used in the light microscope to magnify images of spotted areas of materials or biological specimens. 

Differences between electron microscope and light microscope in a tabular column are available on this page.

Definition of Light Microscopes and Electron Microscopes

A light microscope is a tool used to study microbodies such as bacteria, fungus, etc. to identify their features. Also, it enables examination of small objects which are not visible through naked eyes. The light microscope is also known as an optical microscope. It is an instrument that uses light rays and lenses to enlarge images of microorganisms and other small entities.

One has to place the object on a given platform and view the microbe through the eyepieces. Optical ones are of two types – simple and compound microscopes. The simple one utilizes the visual capacity of single or multiple lenses to enlarge objects. In the case of the compound ones, one lens is placed close to the substance for viewing it.

On the other hand, an electron microscope is an instrument that uses electron beams to capture an image and enlarge it. It is an advanced tool that enables a person to visualise smaller entities in high resolution. Through it, you can magnify things in nanometres and scrutinise the objects carefully.

Though the initial work of both the tools is to magnify objects, there is a difference between light and electron microscope.

Difference between a Light Microscope and Electron Microscope

Multiple Choice Questions

1. The type of electron microscope used for studying the internal structure of cells is

1. Light microscope

2. Scanning electron microscope (SEM)

3. Compound microscope

4. Transmission electron microscope (TEM)

Answer: d

2. The magnification power of an optical microscope is

1. 1500x

2. 4000x

3. 3000x

4. 2500x

Answer: a

3. Under an electron microscope, you can magnify an object up to 

1. 4, 08, 000 times

2. 2, 09, 000 no. of times

3. 3, 00, 000 times

4. 4, 12, 000 number of times

Answer: c

4. The picture taken from a microscope is

1. Monograph

2. Micrograph

3. Pictograph

4. Macrograph

Answer: b

Do It Yourself

Which portion of a compound microscope enables focussing the visible light on the object for a viewing?

From our above text on light mic
roscopes and electron microscopes, we understand that light microscopes use visible light to magnify objects that help us view living and dead organisms without the need of a screen for viewing images. However, electron microscopes use electron beams to view dried and dead organisms on the fluorescent screen.