sound-loudness,intensity,pitch,timbre

                                       SOUND

HOW IS SOUND TRANSMITTED THROUGH A MEDIUM?

Sound is produced by the vibration of the object.Sound needs a material medium to travel.Sound waves are longitudinal waves. In longitudinal waves the particles of the medium vibrates back and forth in the same direction.

Wave length

The distance between two nearest points in a wave which are in the same phase of vibration is called wavelength./ or the distance between the centers of two consecutive rarefactions or two consecutive compressions is called wavelength.

Frequency

Number of vibrations per second is called frequency. Unit Hertz

Velocity

The distance traveled by sound in one second  unit m/s

Velocity v=frequency*wavelength

DIFFERENCE BETWEEN MUSIC AND NOISE

Sound produced by regular vibrations and pleasing to hear is called music

Unpleasant sound produced by irregular vibrations is called noise

 One person feels a particular sound as a music but the other person feels it as noise. So there is personal difference

CHARACTERISTICS OF SOUND

INTENSITY

The amount of sound energy passing each second through unit area is called the intensity of sound.Increasing the amplitude of sound wave increase the intensity.

Intensity of sound is proportional to the square of the amplitude of sound.

Unit W/m^2.

Does the natural frequency of the diaphragm change for the gentle and the strong taps?

The amplitude of vibration changes. But the natural frequency of vibration remains the same.

LOUDNESS

No two persons will not have the same experience of hearing. The intensity of sound produced in the ear is called loudness. Loudness the measure of the response of the ear. loudness is the measure of audibility produced by sound in a person. Unit dB

Factors affecting loudness

Amplitude: Loudness is directly proportional to square of the amplitude of vibrating body.

Surface area: Loudness is proportional to surface area

Distance between source and receiver

 Loudness is inversely proportional to the square of the distance between the source and receiver.

Density of the medium

As density increases loudness increase

If wind is blowing in the direction of propagation of sound loudness increases,otherwise loudness decreases.

PITCH

Shrillness of a sound felt by ear is its pitch.Pitch depends on frequency of sound.

Sounds of higher frequency is called high pitch

sound with lower frequency is called lo pitch

Examples of high pitch sound: Creeping of cricket, sound of woman, sound of children

Low pitch sound:sound of man, sound of drum, sound of beetle,sound of cow

BASS &TREBLE

A group of sound waves of low pitch is bass

A group of sound waves of high pitch is treble

TIMBRE OR QUALITY

This enable us to distinguish one sound from another having the same pitch and loudness.

SOUND OF A PERSON

Loudness is controlled by the flow of air coming from the lungs through larynx.The frequency of sound is controlled by the tension and vibration of larynx. But the quality depends on the resonators.(Nose,moth,throat,empty spaces in side the mouth)

RESONANCE

When a body under forced vibration,if the frequence of the impressed vibration is equal to the natural frequency of the vibrating object, then the amplitude of the vibation is maximum. This phenomenon is called resonance.

Experiments to prove resonance:- Sonometer , Resoanance column

reflection,refraction,total internal reflection,fibre optics

                                 REFLECTION

when a ray of light is incident on a mirror it gets reflected in accordance with the following laws

First law

The incident ray, the reflected ray and the normal at the plane of incidence all lie in the same plane

Second law

The angle of incidence is equal to angle of refraction

LATERAL INVERSION

The sideways reversal of the image formed by a plane mirror is known as lateral inversion

 

 REFRACTION

 The phenomenon of bending of light from its straight line path as it passes from one medium to another with  change in density

LAWS OF REFRACTION

FIRST LAW

The incident ray,the refracted ray, and the normal to the surface of separation at the point of incidence all lie in the same plane.

SECOND LAW

The ratio of the sine of angle of incidence and the sine of angle of refraction is constant  for a given pair of media

sin i/sin r =constant ,This constant is called refractive index(RI)

Another equation for RI= Speed of light in vacuum/Speed of light in medium

On what factors does the refractive index of a medium depend?

Nature of medium

nature of surrounding medium

wavelength of light used

temperature

REFRACTION THROUGH GLASS SLAB

TOTAL INTERNAL REFLECTION

It is the Phenomenon in which a ray of light traveling at an angle of incidence greater than the critical angle from a denser to rarer medium is totally reflected back into the denser medium,obeying laws of reflection

The angle of incidence in the denser medium for which the angle of refraction in the rarer medium is 90'

APPLICATIONS OF TOTAL INTERNAL REFLECTION

1 Sparkling of Diamond

2.Mirage formation

 It is an optical illusion obseved in deserts or over heated surfaces, due to which observer sees a pond of water at some distance. The lower layer of air near earth surface get heated  than the upper layer then at lower layer density of air is less.So refraction take place from rarer to denser medium

LOOMING

This mirage observed in cold region. The lower  layer of air is cooler an denser while upper layer is hotter and rarer. When refraction of light take place the ships appears to hang inverted in the air

3.Optical fiber - Used to transmit light through long distance

4.periscope, binoculars

5.Reflector light of Bicycle

EXPLAIN THE PHENOMENON OBSERVED IN NATURE DUE TO REFRACTION
1. The sun is visible to us about 2 minutes before and actual sunrise

2.A fish at the bottom of the tank appears to be raised its position.

3.AN OBJECT PLACED AT THE BOTTOM OF BEAKER APPEARS TO BE RAISED
4.Twinkling of stars is due to refraction of its light passes through different layers of atmosphere with different densities

LIGHT THEORIES-CORPUSCULAR,WAVE,ELECTROMAGNETIC,QUANTUM,PHTOELECTRIC

                                LIGHT

Different Theories

Corpuscular theory

By Isaac Newton

Light emitted from a source is  the flow of very minute, elastic, invisible , spherical shaped corpuscles. This theory can explain Rectilinear propagation of light,Reflection and Refraction.                                                                                       Newton's fault on explanation of Refraction

Newton argued that the velocity of light increases with increase in density of medium. But Leon Foucault invented light has maximum speed in vacuum

This theory cannot explain Interference, Diffraction and color vision

Wave Theory of Light

By Christian Huygens

Light is propagated in the form of waves. Like sound wave light is also a longitudinal wave also composed of compression and Refraction

This theory can easily explain Diffraction, Reflection, Refraction

 Famous Scientist Thomas Young done a lot of experiments on Optical Phenomenon

Correction of Wave theory

By Augustin Fresnel

Gives a satisfactory explanation of Diffraction, linear propagation based on wave theory. He find out light is Transverse wave instead of longitudinal wave

 Electro magnetic Theory of Light

By James Clark Maxwell

James Clark Maxwell discovered, An electro magnetic wave can propagate as transverse wave in a suitable medium at a speed of  3*10^8 m/s.

Heinrich Hertz confirmed that light is a electromagnetic wave.

This theory cannot explain Photo Electric Effect

Photo electric effect

 light rays, Ultra violet rays, Gama rays falls on certain metal surfaces emits electrons from it. It is discovered by Heinrich Hertz

Quantum theory of light

By Max Planck

 

Radiant energy is not a continuous flow of energy. Energy emitted or absorbed from a light source is in the form of small packet of energy.This packet is called Quantum. A Quantum with definite energy is called Photon

Albert Einstein gives a satisfactory explanation for Photo electric effect based on Quantum Theory

 

         Explanation: When Photons of definite energy falls on the surface of certain metals they collide with electrons present in the atom and that electrons emitted from the surface . One photon can eject one electron.As the intensity of light increases the number of photons increases. as a result more electrons knocked out from the surface of the metal

Dual nature of Light

Light is an electromagnetic wave with particle nature and wave nature at the same time

DISPERSION OF LIGHT,RAINBOW

                              DISPERSION OF LIGHT

COMPOSITE LIGHT

Any light composed of two or more colours is called a composite light

DISPERSION OF LIGHT

Splitting up of a composite light in to its component colours is called Dispersion of light

NEWTON'S EXPERIMENT

 Allow sunlight (To make a narrow beam of light use a mirror and slit)  to fall obliquely on the face of a triangular glass prism.

On the other side we can observe seven colours.Violet colour seems near the base of prism.ie violet deviates more and Red deviate less. From this we can conclude sunlight consist if seven colours. So it is a composite light.

What are the colours formed on the wall?

Violet, Indigo, Blue,Green, Yellow ,Orange ,Red (VIBGYOR). The orderly arrangement of these colours is called Spectrum

Colour                     wave length(nm)

Violet                        400-440

Indigo                       440-460

Blue                          460-500

green                         500-570

yellow                        570-590

orange                       590-620

red                             620-700 

Is there any connection between wavelength and deviation of constituent colours?explain

Yes, When composite light enter from air to prism(glass) there refraction take place.When light emerge out to air from glass there is another refraction take place .According to change in wave length refraction take place at different rates.. According to the difference in wavelength the rate of deviation varies in each colour. The colour with lowest wavelength deviates most. The colour with highest wavelength deviates less. 

Why the light of torch, candle appears yellow instead of white, even though it contain same spectrum of sunlight?

 The intensity of blue color is less in the light of candle and torch . So it appears in yellow. 

CAN WE RECOMBINE THE DISPERSED COLOURS IN THE WHITE LIGHT?

Yes, Arrange the two prisms as shown in figure

                                 RAINBOW

The sunlight that incident at a suitable angle at the top of a water drop undergo two refraction and one total internal reflection inside the water drop. So the white light split in to its constituent colors.

 Why Rainbow appears in Arc Shape?
The line joining the centre of the rainbow and the observsr is called line of vision.Each color of the dispersed sun light  make a definite angle with the line of vision.For an observer from earth can see only one color from a single drop. All water drops appearing in the same colour make the same angle with line of vision.

SELF INDUCTION-MUTUAL INDUCTION- TRANSFORMERS

                    

                                 SELF INDUCTION

 When an AC current flows through a solenoid (an insulated copper wire wound in the shape of a spring) a magnetic field is produced around that wire due to the variation of current in AC ,the magnetic flux around that wire also changes .By Faraday's law of Electromagnetic induction  Whenever there is a change in magnetic flux associated with a closed circuit an induced emf is produced on that wire. This phenomenon is called electromagnetic induction

What is the change in intensity of light of a lamp can be observed when a solenoid connected to AC?

 Due to self induction an emf is produced in the solenoid.This emf always oppose the applied voltage. This emf is called back emf. Due to the back emf the applied voltage decreases .So the bulb glows dimmer.

What is the intensity of light observed if we place a iron core inside the solenoid in the above figure?

The intensity of light is very less. Because the strength of magnetic flux increases when we place a iron core inside the solenoid. So Back emf increases. So it oppose applied voltage . Then the applied voltage decreases

Can we done the same experiment using DC voltage?

No, Electro magnetic induction take place in AC current only

                               MUTUAL INDUCTION

 We can produce an electric current in the second circuit utilizing the current of first circuit even if they are not in direct contact

 

Wind insulated copper wire( wire used for electric motor winding) at one end of a soft iron core and connect its ends to a cell. At the other end of the soft iron core wind another insulated copper wire. Connects its end to a Galvanometer .

OBSERVATIONS

   When the switch is ON and OFF then we can observe a deflection in galvanometer If we keep the switch on for some time there is no deflection in galvanometer

EXPLANATION

 When current flows through first coil magnetic flux is produced around that coil. The second coil is placed in the magnetic field of first one. When the magnetic flux around first coil changes then only an emf is induced on second coil. If we kept the switch on for a while there is no change in magnetic flux linked with second coil because it is DC current. So there is no deflection

When AC current is applied in fist coil. The magnetic flux produced around that wire continuously changes. The second coil is placed in that magnetic field so emf is continuously produced on second coil. This is the working principle of TRANSFORMER

                       TRANSFORMER

 

It is an electronic device to  increase of decrease a given AC voltage. It works in the principle of mutual induction

 There are two types of transformers STEP UP and STEP DOWN

 

               STEP UP TRANSFORMER

Used to  raise a low AC voltage to high AC voltage

Number of turns in secondary coil is greater than that of primary

Thick wire is used in primary coil and thin wire is used in secondary coil

STEP DOWN TRANSFORMER

Used to  decrease high AC voltage to low AC voltage

Number of turns in primary coil is greater than that of secondary

Thick wire is used in secondary coil and thin wire is used in primary coil

If Np is number of turns in primary, Vp is voltage in primary. Ns is the number of turns in secondary, Vs is the voltage in secondary

Vs/Vp = Ns/Np

ELECTRO PLATING

                          ELECTRO PLATING

It is the process of coating a metal on the surface of a conductor by electrolysis. A solution containing the metallic salt is used for this. This is the electrolyte.

Which metal is to be used for electroplating, that metal should be used as the positive electrode, and the solution of the same metal is to be used  as the electrolyte. The object which is to be electroplated is to be used as the negative electrode.

What is the mechanism of electroplating?

When electricity flows through electrolyte changes into ions.it  should contain the ions of the metals to be coated. Metal ions are positive. Therefore the metal ions have a tendency to move towards negative electrode(Cathode) so there we place the object to be coated

Is the DC current is necessary  for electroplating?

Yes,DC is direct current from battery. it has no variation. It always keep anode as positive and cathode as negative. AC is alternating current. So its positive and negative half cycles continuously changes. So the polarity of electrodes continuously changes.

Suppose you you have not a DC supply, But a AC supply is provided how can you produce DC?

Using a Bridge rectifier or center tape rectifier convert AC to DC it is called rectification. Remove resistor from the output and connct the electrodes in that place

Positive electrode       negative  electrode        electrolyte

Anode                            Cathode                        

Metal to coated             Object

Copper                           iron spoon                       Copper Sulphate

Silver                                 "   "                                    Silver nitrate/

                                                                            Silver cyanide+sodium cyanide

Gold                                   "      "                           gold cyanide+sodium cyanide

chromium                          "        "                           chromic acid

Faraday's laws of Electrolysis

First law

The mass of the substance(m) deposited on  an electrolyte is directly proportional to the amount of electric charge(Q) pass through the electrolyte

m=zQ (z is called electrochemical equivalent)

Q=It

Second law

When the same current is passed through different electrolytes, the masses deposited at the electrodes are proportional to their chemical equivalents

If mass m1 and m2  of two different substances of chemical equivalents E1 and E2  are deposited by the passage of same charge Q Then m1/m2=E1/E2

Faraday's constant

It is the ratio of chemical equivalent to electro chemical equivalent 

F=E/z   F=96500 coulomb

It is also defined as the quantity of electricity required to liberate one equivalent mass of the substance during electrolysis

                                       

ELECTROLYSIS-CHEMICAL EFFECT OF ELECTRICITY

        THE CHEMICAL EFFECT OF ELECTRIC CURRENT- ELECTROLYSIS

When electric current passes through a current conducting solution/liquid (electrolyte). The electrolyte decomposes in to its ions .This process is known as electrolysis. This is the chemical effect of electric current.

EXPERIMENT

CuSO4                                                                   carbon rod

Take copper sulphate solution in a beaker. Dip two carbon electrodes in it. Connect these electrodes to a battery. By the passage of electricity the solution decomposes to its ions,ie Cu(2+) ions and SO4(2-) ions are formed. Positively charged copper ions moves towards negative electrode(Cathode). Negatively charged sulphate ions move towards positive electrode(Anode). Sulphate ions move towards anode and looses two electrons. The positively charged Copper ions move towards negative electrode gain two electrons and get deposited as copper atom. We can see this as shiny reddish deposit of Cu on the Cathode.

Why the color of CuSO4 Solution decreases?

Due to the decrease in number of Copper ions in the solution , the concentration of the solution decreases. So the blue Colour of CuSO4 decreases

Instead of Carbon cathode if we use copper electrodes is there any change in bluish color of solution?

 No there is no change in color. The positively charged copper ions move towards cathode and accept two electrons from copper electrode.and deposited there. In the Anode the Cu atom loose two electrons reaches in the solution .So there is no change in concentration of electrolyte.Therefore no change in color.

APPLICATIONS OF ELECTROLYSIS

For electroplating

To purify metals

For anodisation