HOW ARE SPHERICAL MIRRORS MADE AND THEIR TYPES

 

Spherical mirrors are typically made by shaping a reflective material, such as glass or metal, into a spherical shape. The specific method used depends on the material and manufacturing process involved. Here are a couple of common methods for creating spherical mirrors:

1.  Glass Spherical Mirrors:

·         Glass mirrors are often made using a technique called "silvering." In this process, a glass blank is first prepared by grinding and polishing it to achieve a smooth and uniform surface.

·         A thin layer of reflective material, such as aluminum or silver, is then deposited onto the surface of the glass. This can be achieved through various methods, including chemical deposition or physical vapor deposition.

·         After the reflective layer has been applied, a protective coating is typically added to prevent tarnishing or scratching. This coating is often a clear layer of paint or lacquer.

·         The shape of the mirror is determined by the grinding and polishing process, which involves carefully shaping the glass into a spherical form.

SMART WATCHES

1.   Metal Spherical Mirrors:

·         Metal mirrors, such as those made from aluminum or other reflective metals, are often created using a process called "spin forming" or "spinning."

·         A metal disc or blank is placed onto a spinning machine, which rotates the blank at high speeds.

·         As the blank spins, pressure is applied, either mechanically or through the use of specialized tools, to gradually shape the metal into a spherical form.

·         Once the desired shape is achieved, the mirror surface is typically polished to enhance its reflectivity and remove any imperfections.

CONVEX MIRROR USES:

Convex mirrors, also known as diverging mirrors, have several practical uses due to their unique optical properties. Here are some common applications of convex mirrors:

1. Safety and Security: Convex mirrors are widely used for safety and security purposes. They are commonly found in parking lots, garages, and driveways to provide a wide-angle view and eliminate blind spots. They allow drivers to see oncoming traffic or pedestrians, reducing the risk of accidents.

2. Retail and Surveillance: Convex mirrors are employed in stores, supermarkets, and other retail environments for surveillance and theft prevention. By strategically placing convex mirrors, store owners can monitor different areas of the store, minimizing blind spots and deterring shoplifting.

3. Traffic and Road Safety: Convex mirrors are installed at intersections, curved roads, and blind spots to enhance road safety. They provide a wider field of view, allowing drivers to observe approaching vehicles, pedestrians, or cyclists, which helps in preventing collisions.

4. Industrial and Warehouse Settings: Convex mirrors find extensive use in industrial and warehouse settings. They assist in monitoring production lines, machinery operation, and large storage areas where visibility may be limited. These mirrors increase safety by allowing workers to observe their surroundings, including potential hazards or obstacles.

5. Home Security: Convex mirrors can be utilized in residential settings for enhancing home security. By placing convex mirrors strategically near entrances, driveways, or windows, homeowners can monitor activities outside their property and detect any suspicious movement.

6. Decorative Purposes: Convex mirrors are also used for decorative purposes in interior design. They can create an illusion of a larger space by reflecting light and expanding the perception of the room. These mirrors come in various shapes and designs, adding an aesthetic element to the decor.

7. Roadway and Parking Signs: Convex mirrors are sometimes integrated into road signs to provide additional visibility to drivers. They can be used to reflect oncoming traffic or display warnings at blind spots, improving driver awareness and safety.

8. Rearview Mirrors: The passenger-side mirrors in automobiles are often convex to provide a wider field of view. Convex rearview mirrors help drivers see the surrounding traffic, reducing the blind spots and improving overall safety.

CLICK HERE TO SEE CONVEX MIRROR WATCHES 

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GENERAL KNOWLEDGE SECTION : SEARCH AT ONE PLACE.......FIND AT ONE PLACE

 GENERAL KNOWLEDGE - USEFUL for  ALL COMPETITIVE EXAMS...........

PHYSICS

1. From the daily life situation, What is more convenient rolling of stone on a sloping road than to lift it vertical upwards ? 

Ans: the work done in rolling a stone is less than in lifting it. 

2. Which is the phenomenon observed in absorption of ink  by blotting paper?
Ans: Capillary action

3. Give the unit of Nuclear size and it is the name of a scientist.
Ans: Fermi

4.  Why the star appears to move from east to west?
Ans: The Earth rotates from West to East.

5. What is the value of ' one KNOT' ?
Ans: 1.852 Km/hr   and 'knot' is the unit of speed

CHEMISTRY:

1. What is the composition of a soap?

Ans: Potassium and Sodium salts with fatty acids.

2. Say something about 'Selenium'?

Ans: non metal, conductor

3. Which metal remains in liquid form under normal conditions?

Ans: Mercury

4. What is the mass of electron?

Ans: 9.1 X 10 ^ -31 Kg.

5. Which fuel is used in rockets?

Ans: liquid oxygen

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REFLECTION AT CURVED SURFACES - CONCAVE AND CONVEX MIRRORS - A COMPLETE STUDY

SPHERICAL MIRRORS ----  CURVED SURFACES  - KEY CONCEPTS

Let us look at the below diagram, reflection at plane surfaces i.e. at plane mirror. All the laws of reflection at plane surfaces are valid and applicable to spherical mirrors also.

SPHERICAL MIRROR ?

The mirrors which have curved surface are known as Spherical mirrors, these mirrors are part of a hollow glass sphere.

CONVEX MIRROR AND ITS TERMS

The spherical mirror is said to be convex if the bulged surface is made smooth and the inner surface is silvered. 

CONCAVE MIRROR AND ITS TERMS 

The spherical mirror is said to be concave if the bulged surface is silvered and the inner surface is made smooth.

SPHERICAL MIRRORS AND TERMS RELATED :

APERTURE: The surface of the mirror from which the reflection take place is called its aperture.

POLE: The central point on the surface of the mirror is called its pole (P)

CENTRE OF CURVATURE:

The centre of the sphere of which the spherical mirror is a part is called the centre of curvature of the mirror.

RADIUS OF CURVATURE::

The radius of the sphere from which the spherical mirror is a part is called the radius of curvature of the mirror.

PRINCIPAL AXIS:

The line joining the pole and the centre of curvature is called the principal axis of the mirror.

FOCUS: (F)

The point on the principal axis where rays incident parallel to the principal axis converge to reappear or to diverge from after reflection is called the Focus of the spherical mirror.


FOCAL LENGTH (f):

The distance of the Focus from the pole is called the focal length (f) of the spherical mirror.

REAL AND VIRTUAL IMAGES:

An image formed by the actual intersection of light rays is called a real image. A real image is formed on the screen.

If the rays of light responsible for an image do not actually intersect, the image is called virtual image.

Virtual image cannot be formed on the screen, as no light reaches where the image appears to form.

Observe the following ray diagram when a parallel light incidents on a concave mirror and understand the reflection concepts........

 IMAGES FORMED BY A CONVEX MIRROR:

Irrespective of the position of the object , The image formed by the convex mirror is always virtual and erect but when we compare the the size of the image, the image size  is always diminished.  

PRINCIPAL FOCUS OF A CONVEX MIRROR

The principal focus of a convex mirror, which is divergent mirror,  is a point on the principal axis of the mirror, at which all the incident rays parallel to the principal axis appears to diverge after reflection from the mirror.

 The principal focus of the convex mirror is virtual and always lies behind the convex mirror. 

observe the above ray diagram when parallel rays incident on both concave mirror and convex mirror and observe the principal focus. 

from the above ray diagrams, write down the characteristics of the image formed.

MIRROR FORMULA:

1/v + 1/u = 1/f

From the mirror formula, if we observe, we can understand that how the object distance,u, and image distance,v, are related to the focal length.  The distances are measured from the pole only. Pole to object is u, and pole to image is v, 

MAGNIFICATION BY SPHERICAL MIRRORS:

Generally, we can understand that the magnification is the increase in the image size with respect to the size of the object which is produced by spherical mirrors.  The magnification is calculated by taking the ratio of height of the image to the height of the object ---- hi/ho.  It can also be calculated by the negative ratio of the image distance to the object distance.

 What can we understand from the magnification ?

*** when 'm' value is positive it tells us image is virtual.

*** when 'm' value is negative it tells us image is real.

logical question combining mirror formula and magnification

FIND OUT THE OBJECT DISTANCE (u), when the magnification produced is 'm' and focal length is 'f'.

solution:    

mirror formula is :  1/f = 1/v + 1/u

  magnification is m = -v/u   so  v=-mu

substituting the 'm' value in formula:

  1/f = 1/-mu   + 1/u

1/f = 1/u(1/-m + 1/u)

    simplifying,   u = f/m(m-1)

critical thinking problems:

1. Suppose that you are given a concave mirror of focal length 15 cm.  Then, 

a) To get the magnification m=1, where the object is needed to be placed
b)  When the object is placed at 30 cm, write the characteristics of the image formed.
c)  Your friend told that the image formed at infinity, where would be the object is placed.

2. When a student is performing experiment with concave mirror of focal length 20 cm, then he observed that the size of the image is reduced to 1/3rd of its size of the object.  Calculate the object distance in this situation. 

  

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COMPLETE STUDY MATERIAL ON CHEMICAL EQUATIONS - FOUNDATION TO ADVANCED

CHEMICAL REACTIONS - CHEMICAL EQUATIONS

INTRODUCTION:

In our daily life we all know about physical changes and chemical changes, all these changes are observed in our day today life.  We observe ice converts into water vapor and vice versa.  In this example, the changes in the states of matter are observed and heat may be gained or released.  Similarly, burning of wood also example.

CHEMICAL REACTION:

 Chemical reactions represent the processes in which a single substance or substances undergo change to produce new substance or substances with different or new properties are called 'CHEMICAL REACTIONS'.

For example: When potassium nitrate gets heated potassium nitrite and oxygen are formed.  This is a chemical reaction since potassium nitrate changes into potassium nitrite and oxygen, these are new substances.

A chemical reaction consists of REACTANTS and PRODUCTS.

From the above example, potassium nitrate is called Reactant and potassium nitrite and oxygen are the products, since the substance which takes part in  chemical reaction is called Reactant and a new substance formed or substances formed in a chemical reaction, called products.

FIND OUT THE REACTANTS AND PRODUCTS from the following:

Calcium carbonate ----->  Calcium oxide and carbon dioxide

Sodium combines with water to get sodium hydroxide and hydrogen

HOW THE REACTANTS ARE TRANSFORMED INTO PRODUCTS ??????

Initially, the compounds or molecules break down into atoms and these atoms take part in the reaction then products are formed by new bonds formed between the atoms.

CHARACTERISTICS OF CHEMICAL REACTION:

How can we understand that there is a existence of chemical reaction and it took place, by observing the characteristics we can understand that there is a chemical reaction observed ......

1) When metals react with acids, we can observe there is evolution of Hydrogen gas.

2) Formation of precipitate when two solutions are mixed, the precipitate is a solid substance separated from the solution.  For example, lead iodide is a precipitate formed when lead acetate aq.solution combined with aq. sol. of potassium iodide.

3) Some times we observe the emission of heat such reactions are exothermic reactions, we know that when Calcium oxide is added to water, and sometimes the equipment becomes cold when ammonium chloride mixed with barium hydroxide.  These are called endothermic reactions.

CHEMICAL EQUATIONS  Vs CHEMICAL REACTIONS

We can understand with an example :

CaCO3 is the formula of Calcium carbonate and CaO is calcium oxide and CO2 is carbon dioxide.

The above is a chemical reaction, when it is represented with formula and symbols, that notation is known as chemical equation.

How can we write a chemical equation ??????

* the reactants and products in the reaction should be written with their formulae  or symbols.

* when more than one reactant or product, then + symbol is used

* an arrow mark is used in between reactants and products, the arrow mark also tells us in which way the reaction is taking place.

What information is conveyed by a chemical equation ???


* we understand the reactants and products in the reaction, and their number of atoms

* we can calculate the masses of the compounds or molecules in the reactants and products

* we come to know the number of moles of the reactants and products.

EXAMPLE:

               When we observe the formation of water from hydrogen and oxygen :

There are :

four hydrogen atoms, two oxygen atoms gives two water molecules

two moles of hydrogen and one mole of oxygen to give two mole of water

four grams of hydrogen and thirty two grams of oxygen to give 36 g of water

we can also calculate number of atoms and volumes also.

             2 H2 + O2 ------> 2 H2O

HOW TO MAKE A CHEMICAL EQUATION MORE INFORMATIVE ???

Generally,  a chemical equation do not represent any thing other than the reactants and products, but to make a chemical equation more informative, one has to represent :

* states of the reactants and products, s, l, g, aq.

* the evolution of gas with upward arrow line and precipitate with downward arrow line

* if heat is liberated, then in the products + heat should be written

* if heat is absorbed, then in the reactants + heat should be written.

TYPES OF CHEMICAL REACTIONS:

1) COMBINATION REACTIONS

2) DECOMPOSITION REACTIONS

3) SINGLE DISPLACEMENT REACTIONS OR SUBSTITUTION REACTIONS

4) DOUBLE DISPLACEMENT REACTIONS


WHAT IS THE DIFFERENCE BETWEEN BALANCED CHEMICAL EQUATION AND UNBALANCED CHEMICAL EQUATION ??


BALANCED CHEMICAL EQUATION : When the number of atoms of each element on both sides is  equal then the equation is said to be balanced chemical equation.

UNBALANCED CHEMICAL EQUATION: When the number of atoms of each element on both sides is not equal, then the equation is said to be unbalanced chemical equation.

HOW TO MAKE AN EQUATION A BALANCED EQUATION - STEPS TO BE REMEMBERED:

** must know the formulae of compounds or molecules of reactants or products and the subscriptions in the formulas should not be altered at any cost.

for example: always the calcium carbonate is CaCO3 and Hydrogen molecule  is H2 only.

TRIAL AND ERROR METHOD OF BALANCING A CHEMICAL EQUATION:


STEPS:

1) COUNT EACH TYPE OF ATOMS ON BOTH SIDES

2) IDENTIFY THE MOST COMPLICATED FORMULA AND COUNT THE NUMBER OF ATOMS OF EACH ELEMENT

3)  BY TRIAL AND ERROR METHOD, CHANGE THE NUMBER OF ATOMS ON BOTH SIDES TILL THE NUMBER OF ATOMS ON BOTH SIDES EQUAL.

EXAMPLES OF UNBALANCED AND BALANCED EQUATIONS:

1) KClO3 ---> KCl + O2

 After balancing,

   2KClO3 ----> 2 KCl + 3 O2



2) CaCO3 ---> CaO + CO2



 3) AlCl3 + Ca(OH)2  ----> Al(OH)2 + CaCl2


    2 AlCl3 + 3 Ca(OH)2  ----> 2 Al(OH)2 + 3 CaCl2

4) Al + H2SO4 ----> Al2(SO4)3   +  H2

After balancing:

2 Al + 3 H2SO4 ----> Al2(SO4)3   +  3 H2

How to balance a chemical equation? with algebraic expression method.

A chemical equation tells us the type of reaction between different reactants. Chemical equation gives the states of the reactants and products.  One can calculate the amount of products required for required amount of products.

To balance a chemical equation, very interesting method is algebraic expression method.


for example:  C3H8 + O2 -----> CO2  + H2O




The above reaction is to be balanced using algebraic expressions

step 1) the coefficients of Each reactants and products assumed to be a,b,c,d,...

                    aC3H8 + b O2 -----> c CO2  + d H2O

step 2) identify and count the number of elements on both sides of the reaction

                    carbon: 3a = c

                    hydrogen: 8a = 2d

                    oxygen:  2b = 2c + d

                    

step 3) let us assume a=1, then simplify the equations for other variable values

                        c = 3,     2d = 8   then d = 4             if d=4 and c =3 then 2b=6 + 4 = 10, b=5

step 4) write the chemical equation using the variable values

            C3H8 + 5O2 ---> 3CO2  + 4 H2O



step 5) count the number of atoms on both sides

                   carbon atoms  = 3
                  hydrogen atoms = 8
                  oxygen atoms = 10 





step 6) we conclude that the equation is said to be balanced. 

ASSIGNMENT ON BALANCING CHEMICAL EQUATIONS:

1) Reaction between Iron oxide and carbon to get Iron and carbon dioxide

2) reaction between hydrogen and oxygen to get water

3) reaction between acetic acid and ethyl alcohol to get ethyl acetate and water

4) when sulphuric acid reacts with calcium carbonate to get calcium sulphate along with H2CO3

5) combustion of methane to get carbon dioxide and water

6) reaction between copper oxide and sulphuric acid to get copper sulphate and hydrogen

7) reaction between nitrogen and oxygen

8) reaction between ammonia and oxygen

9) reaction between nitrogen and hydrogen

10) when ammonia reacts with hydro chloric acid to get ammonium chloride

11) when sodium reacts with water to get sodium hydrogen and hydrogen

12) when calcium reacts with hydro chloric acid to get calcium chloride and hydrogen

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LABORATORY APPARATUS - USES

LABORATORY APPARATUS - HOW TO USE AND WHAT ARE THEIR ADVANTAGES ?

1, I am ‘Test tube’…..!

A test tube is a clear glass or plastic container that is much longer than its wide, commonly has a U-shaped bottom and has an open top.  Glass and special plastic test tubes are also non-reactive.  Many metals react with all sorts of chemicals in ways that would ruin an experiment or sample. 

Chemists use test tubes to mix, heat and/or hold small quantities of chemicals for assays and laboratory experiment.  Biologists use them to culture and handle various organisms, fluids, and samples.

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2.  I am ‘Beaker’

 

A Beaker is a common container in most labs.  It is used for mixing, stirring, and heating chemicals.   It is generally a cylindrical container with a flat bottom.  Most also have a small spout to aid pouring.  Beaker is distinguished from a flask, by having straight rather than sloping slides.  Beakers are available in glass, and also in metal, plastics.  

Any experiment which yields a liquid product uses a beaker to catch the liquid.

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3. CONICAL FLASK

SK’mCAn Erlenmeyer flask also known as a Conical Flask or a titration flask, which features a flat bottom, a conical body, and a cylindrical neck.  It is named after the German Chemist Emil Erlenmeyer (1825-1909), who created in 1860.

Erlenmeyer flasks have wide bases, with sides that taper upward to a short vertical neck.  They may be graduated, and often spots of ground glass or enamel are used.  It differs from the beaker in its tapered body and narrow neck.  Depending on the application, they may be constructed from glass or plastic in a wide range of volumes. The mouth of the Erlenmeyer flask may have a beaded lip that can be stopped or covered.

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4.  I am watch glass….

A watch glass is a circular concave piece of glass used in chemistry as a surface to evaporate a liquid., to hold solids while being weighted, for heating a small amount of substance and as a cover for a beaker.  It can be used to prevent dust or other particles entering the beaker, the watch glass does not completely seal the beaker, so gas exchanges still occur.  When used as an evaporation surface, a watch glass allows closer observation of precipitates or crystallization.

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5. PIPPETTE

Pipette or pipet is a laboratory tool commonly used in chemistry, biology, and medicine to transport a measured volume of liquid. 

Pipette works by creating a partial vacuum above the liquid –holding chamber and selectively releasing this vacuum to draw up and dispense liquid. 

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6. RUBBER STOPPERS

•Rubber stoppers in the labs are used frequently to plug flasks and test tubes.  Its purpose is to prevent liquids, and gases, escaping from their containers and also to prevent contaminants from entering the containers.
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7. ROUND BOTTOM FLASK/ROUND BOTTOMED FLASK

   

   A GLASS FLASK USED IN LABORATORY FOR HOLDING CHEMICAL LIQUIDS AND SOLUTIONS, WHICH HAS A SPHERICAL SHAPE BODY FOR UNIFORM HEATING AND HAS CYLINDRICAL NECK. IT IS ALSO KNOWN  AS A BOILING FLASK, MOST OFTEN USED WHEN HEATING SOLUTIONS, PARTICULARLY FOR DISTILLATION. 

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8. FUNNEL

Glass funnels can be used to guard against spillage when pouring chemicals from one vessel to another, can be fitted with filter to separate solids from liquids. 

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9. GRADUATED CYLINDER

•A graduated cylinder also called as measuring cylinder, used to measure the volume of liquids.  It is used accurately to measure the volume of chemicals for use in reactions.

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