Category: Physics Notes PPT

The boundary that is of the region from which no escape is possible is known as the event horizon. Although we can say that the event horizon has an enormous effect on fate along with the circumstances of an object that is crossing it. according to relativity that is the general relativity theory it has no locally detectable features. 

In many other ways also a black hole acts like an ideal body or the black body as it reflects no light.  Moreover we can see here that the quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation. 

Note: Along  with the same spectrum as the body which is black of a temperature inversely proportional to its mass. This temperature which we look at here is on the order of billions of kelvin for holes which are black of mass stellar that is making it essentially impossible to observe.

How are Black Holes formed?

The Michell’s which are simplistic calculations assumed such a body might have the same density as that of the Sun and concluded that such a body which would form but dampened enthusiasm which when the wavelike nature of light became apparent in the early century which is of nineteenth.

If the light which we see was a wave rather than a “corpuscle” it is then very unclear what if any of the influence of gravity would have on the escaping wave of light.  Modern physics very promptly discredits the notation of Michell’s of a light ray shooting directly from the surface to that of a star which is supermassive. the being which slowed down by the gravity of the star’s which is stopping and then free-falling back to the star’s surface.

What are Black Holes?

The gravity is also so strong because the matter which we have been discussing has been squeezed into a tiny space. This can happen at the specific time when a star is dying.

Because of the fact that no light can get out the people can’t see black holes. They are invisible in nature. The telescope or the Space telescopes with special tools can help find black holes. The tools which are very special can see how stars that are very close to black holes act differently than other stars.

 

Phenomenon of Black Holes

The phenomenon of Black holes can be small or big. According to the Scientists they think that the smallest black holes are as small as just one atom. These black holes are very tiny in size but have the mass of a mountain which is very large. The Mass is the amount of matter or we can say the stuff that is in an object.

Another kind of black hole is known as the  “stellar.” The mass of the mass can be up to 20 times more than the mass of the sun which is in the solar system. There may be many many stellar masses which are of the black holes in the galaxy of Earth’s. The galaxy of Earth’s  is known as the Milky Way.

The black or the largest black holes are known as the  “supermassive.” These black holes have masses that are more than 1 million together sunsin the system. Scientists have already found proof that every large galaxy contains a supermassive black hole at its center. The blavk hole which is a supermassive hole at the center of the Milky Way galaxy is known as Sagittarius A. It has a mass equal which is approximately  about 4 million suns and would fit inside a very large ball that could hold a few earths million in number .

How are Stellar Black Holes Formed?

Scientists already think that the smallest black holes formed when the universe began.

The black holes of the Stellar are made when the center of a very big star falls in upon itself or we can say they collapse. When this happens it causes a supernova. A supernova phenomenon is an exploding star that blasts part of the star into space.

According to the Scientists, the supermassive black holes were made at the same time as the galaxy they are in.

The Black holes which are discussing here do not go around in space eating stars planets and the moons. The Earth will not fall into a black hole because no black hole is close enough to the solar system.

Even if we talk about the  black hole mass as the sun were to take the place of the sun, the planet Earth still would not fall in. The black hole that would have the same gravity as that of the sun. the planet Earth and the other planets along with it would orbit the black hole as they orbit the sun now.

The sun is said to never turn into a black hole. The sun which is in the solar system is not a big enough star to make a black hole all alone.

                                               

An incandescent bulb gives us light and an incandescent lamp or incandescent light globe is an electric light with a filament wire that is heated until it glows. The current is supplied to the filament by the means of wire or the terminals embedded in the glass. A socket bulb generally provides mechanical support and electrical connections as well.

The bulbs which are incandescent are manufactured in a wide range of sizes. That is the output of light and voltage ratings that is from 1.5 volts to about 300 volts. 

As a result, we can say that the incandescent bulb became widely used in household and commercial lighting that is for portable lightings such as lamps on tables and the car headlamps and flashlights and for advertising and decorative lighting.

Light Bulb

A bulb that generally gives out or we can say it emits light. There are different types of bulb in varieties. The bulb which is the filament one is used, for example, in a car headlight or for lighting in houses purpose as well.  There are also lights that are fluorescent and they are energy saving in nature. Another type is an LED is a light-emitting diode. These are getting more popular nowadays in the day to day life. For example, we can see an array of LEDs in brake lights of vehicles.

A simple traditional light is an incandescent bulb. This is such a basic technology that we take this almost for granted but if we delve into the quantum physics that is behind it we find that something amazing is happening with it.

The principle that is operating behind the light bulb is very simple: we run an electric current through a thin filament which causes it to get hot. The objects that are hot generally emit light so the bulb glows. The higher the temperature the more intense the glowing of the bulb happens and the more “white” the light that comes out. So we can say that if we get the filament hot enough then we get a bright source of light at wavelengths through the whole visible region of the spectrum.

LED Light Bulbs

As we have seen that the high temperature is the reason for the lighting of the bulb. The Heating of a filament to the temperature that is necessary for air will cause chemical reactions that quickly destroy the filament. This can be avoided by usually putting the filament in a glass bulb with the air either pumped in it away or in a higher-wattage bulb replaced with an inert gas for example like argon. This is why if we put a light bulb in a microwave oven sometimes it produces cool flickering colours that represent the gas inside makes a plasma.

The light which is emitted by a hot object is known as “blackbody radiation,” and has some interesting properties which are simple. The colour of the light does not strongly depend on the properties of the material being heated that are just its temperature. And the spectrum of light or the intensity of the light emitted at various wavelengths usually takes the form of a broad peak whose wavelength changes location in a fairly simple way. 

This makes the spectrum surprisingly difficult to explain though. As we have mentioned when writing about Sir Einstein’s truly radical contribution to Physics, the most obvious approach to this problem generally produces disastrous results. Sir Max Planck was able to explain the spectrum in 1900 but he had to resort to maths for a desperate trick that is assigning an energy characteristic to the light-emitting material. This is the idea Sir Einstein picked up in 1905, which is introducing what we now call photons in order to explain the photoelectric effect. These LED models are inevitable to the development of quantum mechanics in all its glory.

Halogen Bulbs

A lamp of halogen is also sometimes called a halogen of the tungsten that is quartz-halogen or we can say quartz iodine lamp is a lamp that is incandescent. That consists of a filament of tungsten which is sealed into a compact transparent envelope. The envelope is filled with a mixture of a gas that is inert and a small amount of a halogen gas such as bromine or iodine. This allows the filament to operate at a temperature that is higher than a standard incandescent lamp of similar power and life operating. This is also said to produce light with higher luminous efficacy and temperature colour.

Generally, a telescope is a device used to observe space, Stars, etc. It is manufactured in different mirrors like convex, concave, and their combination, etc. Earlier, we refracted telescopes. But these were replaced entirely by the Cassegrain reflector telescope by providing sharp and high contrast images. Let us understand the working principle of a Cassegrain reflector telescope.

Working Principle of Cassegrain Reflector

The Cassegrain reflector works on a unique principle to give images effectively. Generally, the Cassegrain reflector is designed to combine one primary concave lens and one secondary convex lens. Also, a mirror is replaced in the place of the lens in its design. With the presence of a mirror, which is lightweight, the Cassegrain reflecting telescope produces parabolic aberrations instead of spherical aberrations. The parabolic Miller has a hole in its Center, and from there, the electromagnetic waves were captured and sent to secondary convex lens edges in hyperbolic form. 

As the name of our telescope itself tells that it has a reflection, the received electromagnetic waves were sent back to the hole, which is termed as an eyepiece and reaches the focal point. The two-way direction of electromagnetic waveforms a fold at the focal point. This force gives the highest focal length and bright, sharp magnetic image than any other telescope.

Classification of Cassegrain Reflecting Telescopes

There are two types of casa grande reflecting telescopes. Both of these telescopes have very slight differences. They are – 

1. Maksutov-Cassegrain Telescopes: these are also known as Mak telescopes. In these telescopes, a simple spherical curve will be there for the primary lens, and the secondary lens has a thin layer of aluminium. This type of telescope was easy to design and manufacture. It doesn’t require any alignment and is also compact and versatile with very few chromatic aberrations.

2. Schmidt – Cassegrain Telescopes: these are known as SCTs. It is an ideal method used by many people to explore the sky and planetary systems, which is specially designed and placed a figure lens at the starting part of the tube. Also, placing a piece of fulfilment at the plane gives a large aperture.

Advantages of Cassegrain Reflecting Telescope

The Cassegrain reflecting telescope has several benefits because of its nature. Some of those benefits are – 

• In this telescope, the mirror is replaced by an objective lens. So there is no chance for chromatic and spherical aberrations.

• The spherical aberration will be converted into parabolic aberration.

• The appearance of the image in a reflecting telescope is brighter than that of the refracting telescope.

• Another advantage of a Cassegrain reflecting telescope is, it requires only one side of polishing the image.

• The lens is heavier than the mirror. So because of using lightweight mirrors, the apparatus requires less support.

These are some of the advantages possessed by a Cassegrain reflector.

Newtonian Cassegrain Telescope

Whenever we hear the name of Isaac Newton, we always remember gravitational force. He also worked on the light and its waves. In this process, he got mixed up with using a refracting lens. He wants to avoid chromatic aberrations and wants to try something different than the refracting lenses. 

He tried to use a copper and tin mirror instead of placing a lens as it is very cheap and produces tons of light with more sharpness and brightness. In the Newtonian Cassegrain telescope, the light is collected at the top of the tube and the other endpoints towards the sky. The lower part of the telescope will be in a spherical or parabolic shape. The celestial bodies emit the waves.

The image captured by the primary lens can be reflected in the secondary lens and vice versa. This can be done with a 90° angle. The whole experiment was done in the 16th century. How wonderful it is! Still, everyone is eager to use the principle as well as the telescope.

Conclusion

Hence the Cassegrain reflector is an ancient model used to detect the images from sky, Stars, planets, etc., at an affordable price. Several scientists did experiments and found new things which are beneficial to future generations. So everyone should understand the value of these studies and make worth of these experiments.

The measure of electric charge accumulated in a particular field is called charge density. We can determine it in terms of volume, area, or length. We can divide the charge density formula into three types depending on its nature: (i) Linear (ii) charge density ( λ ) (iii) Surface charge density ( σ ) (iv) Volume charge density ( ρ ). Volume charge density is the quantity of charge per unit volume. Charge density measures the electric charge per unit measurement of the space. The space of measurement may be one, two, or three dimensional. Like mass density, charge density also varies with position. Thus, it can be positive or negative.

What is Linear Charge Density?

The quantity of charge per unit length, measured in coulombs per meter (cm−1), at any point on a line charge distribution, is called linear charge density (λ).

Suppose q is the charge and l is the length over which it flows, then the formula of linear charge density is λ= q/l, and the S.I. unit of linear charge density is coulombs per meter (cm−1).

Example: 

Q. A 50cm long thin rod has a total charge of 5mC uniformly distributed over it. What is the linear charge density?

Solution: q = 5 mC 

      = 5 × 10-3 C

l = 50 cm = 0.5 m 

             We have to find λ.

We know,

    λ = q / l  

       = 5 × 10-3 / 0.5

       = 10-2 c⋅m−1

What is Surface Charge Density?

The quantity of charge per unit area, measured in coulombs per square meter (Cm−2), at any point on a two-dimensional surface, is called the surface charge density(σ).

Suppose q is the charge and a is the area of the surface over which it flows, then the formula of surface charge density is σ = q/A, and the S.I. unit of surface charge density is coulombs per square meter (cm−2).

Example:

Q. A sphere has a charge of 12 C and radius 9 cm. Calculate the linear charge density?

Solution: Given,

Charge q = 12 C,

Radius r = 9 cm.

The surface charge density formula is given by,

σ = q / A

A=4 π r2

A = 4 π (0.09)2

A = 0.1017 m2

Surface charge density, σ = q / A

σ = 12 / 0.1017

  = 117.994

Therefore, σ = 117.994 cm−2

What is Volume Charge Density?

The quantity of charge per unit volume, at any point in a three-dimensional body, is called volume charge density(ρ).

Suppose q is the charge and V is the volume over which it flows, then the formula of volume charge density is ρ = q / V and the S.I. unit of volume charge density is coulombs per cubic meter (C⋅m−3)

Example

Q.A sphere of radius 1.85 cm has a charge of -260e spread through the volume uniformly. The sphere has a volume charge density of?

Solution: We are given,

The charge in the sphere, Q=−260e

The radius of the sphere, r=1.85cm

If Q is the total charge distributed over a volume V, then the volume charge density is given by the equation:

ρ= Q/V

The volume of a sphere:

V= 4/3πr3

The volume charge density of the sphere is:

ρ = Q / (4/3)πr3

  =−260e×3 / 4π(1.85cm)3

  =−9.8ecm−3

(Image to be added soon)

Solved Examples

1: Calculate the Charge Density of an Electric Field When a Charge of 6 C / m is Flowing through a Cube of Volume 3 m3.

Solution: Given the parameters are as follows,

Electric Charge, q = 6 C / m

Volume of the cube, V = 3 m3

The volume charge density formula is:

ρ = q / V

ρ =6 / 3

Charge density for volume ρ = 2C per m3.

2: Find the Volume Charge Density if the Charge of 10 C is Applied Across the Area of 2m3.

Solution: Given,

Charge q = 10 C

Volume v = 2 m3.

The volume charge density formula is,

ρ = q / v

ρ = 10C / 2m3

ρ = 5C/m3

Everything we observe around us has some appearance, some objects have an emerald green colour, some are golden yellow, while some have a classic blue colour, and so on.

Do you know why we experience this distinction? It’s because each of these colours has a particular wavelength in the light spectrum and that the reflection of these fall onto our eyes. So, colour is the wavelength of light on the visible spectrum. 

In this article, we will discuss colour, the colour of rainbow, and colour combinations, etc.

What is Colour? 

Colour is the reflection of the light of any object onto the eye. We can describe colour in terms of hue, lightness, or saturation. In physics, colour is associated more specifically with electromagnetic radiation or EM waves of a certain range of wavelengths visible to the human eye. Radiation of such wavelengths that a human eye can pertain to is that portion of the electromagnetic spectrum, which we commonly call the visible spectrum, viz:  the light.

A colour that forms a band of seven colours is called the spectrum, where spectra mean seven and naturally, we can see this effect as a rainbow during rainy seasons. Now, we will understand the colour of the rainbow.

Colour of Rainbow

We all observe a spectrum of different colours that give a beautiful scenic view to the sky during the rainy season. Do you know what this beautiful scenic view is called? Well! It’s a rainbow. 

A rainbow is a collection of colours where each colour carries its own wavelength and frequency. 

Starting from Violet having the least wavelength and high frequency, then indigo, blue, green, yellow, orange, and red with low frequency and high wavelength.

So, the combination comes as VIBGYOR. Here, VIBGYOR is rainbow colours in order. Now, let’s see the range of these lights on the visible spectrum:

Colour Wheel

Each and every colour present on this planet carries its own existence. We categorize its existence by wavelength and frequency and let’s do this part followed by various colour combinations.

Now, we will the wavelength of primary colour wheel in Angstrom:

Primary Colour Wheel

An Angstrom or Å is equivalent to the 1/10,000,000,000 of a meter. The atom-like hydrogen measures approximately one Å. The wavelength of optical light generally ranges from 4500 Å to 7000 Å. Below are the various kinds of light wavelengths and frequency given in Å.

Colour Combinations

When two or more colours are combined, we get various combinations that are distinctive in nature. A human eye is the gifted optical lens that can easily distinguish among 1000+ shades of a single colour.

If we talk about a Primary colour wheel, Red, Green, Blue is taken as primary colour combinations. 

Different colours we find in our surroundings like mauve, navy blue, teal colour,  turquoise colour, colour burgundy, coral colour, dark green, light green, crayon colours are all colour combinations.

Now, let’s look at some eye-catching colour combinations for the year 2021 and the colouring of these can be done by using a watercolour:

Combination 1 – LIVING CORAL #FC766AFF & PACIFIC COAST #5B84B1FF

 

                        

Living Coral is a lively, nourishing colour that has a youthful flavour in it. On combining it with the refreshing blue of the Pacific Coast, it elicits images of the ocean floor and a vibrant seabed filled with coral.

Pacific Coast is a deep colour that subtitles the tone of Living Coral. Akin to most shades of blue, there is almost a certain warmth in this colour. This reason serves to bring the peace and energetic vibe of Living Coral.

Combination 2 – Blue #00A4CCFF & Orange #F95700FF

               

The classic combination of blue and orange has always been in its higher position over the years, The cool and calming tones of blue emphasize the warmth that orange radiates. This pairing is more often found in nature, it is also meant to be comfy and familiar to the human eye.

From nature to the communication perspective, this colour combination has been used in uncountable posters, adverts, and commercial campaigns, and many more places over the years. 

This combination never dies, in fact, it is an effective method of catching an audience’s eye.

How does electricity conduct in liquids? We know that under solids metals are the best electricity conductors. That is due to loosely held outermost mobile electrons that move from one atom to another. On the contrary, electrons in a chemical bond of liquids are static. Charges introduced by dissolving compounds in the water are responsible for the conduction of electricity in liquids. In water, the chemical bond of compound breaks into numerous atoms carrying a positive or negative charge on it. Freely moving charges flow resulting in electrical conductivity.

Electrolysis or How do Liquids Conduct Electricity?

The phenomena of chemical decomposition of liquid or solution constituting ions when electricity passed through it are called electrolysis. The compounds which break its chemical bond in water are called Ionic compounds. Are you thinking of an example; Sodium Chloride is an excellent example of an ionic compound. Atoms carrying charges are called Ions. Positive charge-carrying ion is called cations. Negative charge-carrying ions are called anions. Now if you mix Sodium Chloride in water, freely moving ions are formed. Cations travel to a negative electrode to collect electrons. Anions navigate to the positive electrode and donate its extra electrons.

If you have a query in your mind – what happens when electricity passes compounds in the molten state, then here is the answer – molten metal compound splits into single component form and gets accumulated at electrodes. Gases released as the result of this chemical reaction dissipates in the air. Now let’s move ahead and understand what happens when electricity passes in water.

Now let’s move ahead to understand what happens when electricity passes in water.

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Image of electrolysis of water displaying split of water in hydrogen and hydroxide ion moving towards cathode and anode respectively to release hydrogen and oxygen gas.

Electrolysis in Water

Let’s observe how electrolysis of water happens. The water dissociated into hydrogen and oxygen gas when the electric current passed through it. An electronic source connected to an inactive electrode like platinum immersed in water. Does pure water conduct electricity? Pure water is the best insulator. Therefore, an electrolyte was added to improve the conductivity of pure water. When electric power passes, the water separates into positive hydrogen ions and negatively charged hydroxide ions. Now, what happens to the charged ions?

H₂O = 2H⁺ + OH⁻

The two charged ions traverse towards opposite electrodes. Electron transfer from a negatively charged electrode, i.e. cathode to hydrogen ion leading to a reduction of the cathode. Whereas the positively charged electrode, i.e. anode gains an electron from hydroxide ion resulting in oxidation of anode.

Reduction at Cathode

The hydrogen ions move towards the cathode. These positive cations gain an electron from the cathode and convert into stable hydrogen gas.

H₂O = 2H⁺ + OH⁻

 

2 H⁺(aq)+ 2e⁻ → H₂(g)

Oxidation at Anode

Whereas, the negative hydroxide anion moves towards the anode. This negative anion loses an excess electron to the electrode and converts into stable oxygen gas.

4 H₂O → 4 OH⁻(aq) + 4 H⁺

4 OH⁻ (aq) → O₂ (g) + 2 H₂O (l) + 4 e

The ratio of generated oxygen and hydrogen molecules is 2:1. The electrolysis of water produces one molecule of oxygen for every two molecules of hydrogen. Thus twice the volume of hydrogen is generated as a result of water electrolysis. 

Testing the electrical conductivity of liquids can be done by the same mechanism. Take a fluid in a container which has two electrodes connected to battery and bulb. The glowing bulb will indicate that fluid is a good conductor of electricity.

Benefits of Electrolysis

Generation hydrogen for fuel, or the production of electric power using fuel cells 

• Production caustic soda from the concentrated saline solution.

• One of the most critical uses of electrolysis is the production of heavy metals like aluminium, sodium, calcium. During the electrolysis of molten compounds, heavy metals get precipitated at the electrode. Precipitated metal is collected and used for different industrial purposes.

• Another important use of electrolysis is the coating of one metal over another. The method used to coat a metal over another is called electroplating. The object to be coated with metal is used as a cathode. The anode is made of metal used for coating. The electrolyte is the soluble compound of metal to be coated.

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Image of the basic setup of electroplating to coat spoon which is made as cathode ,whereas anode is made of the metal which is used for coating.

Fascinating and Fun Fact with Regards Conduction of Electricity in Liquids

• Stainless steel cutleries in our kitchen like the spoon, fork, etc. are coated with copper by the process of electrolysis.

• Utensils used in the religious places is electroplated to convert into expensive silver utensils.