Activity 1 : Faraday's Law

 [to be done in practical sheets]

Activity 1: TO STUDY FARADAY LAW OF ELECTROMAGNETIC INDUCTION

REQUIREMENT: Phet simulation

THEORY

[Write in details about Faraday law of electromagnetic induction in detalis with figure]

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PROCEDURE

[this is instruction for you, you should convert these instructions in to third person passive form]

1. Visit phet simulation website and open the Faraday's law simulation.

2. Observe the screen and find the different control icons to change the  number of loops in the coil, to change the polarity of magnet etc.

3. Pick up the magnet and insert in the coil and observe the deflection in voltmeter ( check the voltmeter and field lines box).

4. Next change the polarity of the magnet and observe the change in direction of deflection in voltmeter.

5. Change the speed of movement of magnet and observe the difference in amount of voltage induced.

6. Repeat the observation for amount of voltage by inserting the coil with same speed in  few turns and then coil of many turns.

OBSERVATION

Table 1: Observation of cause of electromagnetic induction

S.N	Action	Observation	Remarks
1	Magnet inserted in the coil	Field lines changes in the coil	Deflection occurs
2	Magnet kept at rest inside the coil	Field lines doesn't change	Deflection doesn't occurs
3.	Magnet taken out from coil	………………..	…………………….

Result 1. ………………………………………………………………………………….

Table 2: Observation for direction of current induced 

S.N	Action	Observation	Remarks
1	North pole of magnet inserted in coil	Deflection is in ........(right/left) side	Current in induced in one direction
2	South pole of magnet inserted in coil	Deflection is in ........ side	Deflection occurs in opposite direction

Result 2: Direction of induced current depends upon the direction of magnetic field.

Table 3: Observation for amount of current induced current with the speed of motion

S.N	Action	Observation	Remarks
1	Magnet moved slowly	Deflection is ......... unit	.........(more/less) current is induced
2	Magnet moved quickly	Deflection is .......unit	........(more/less) current is induced

Result 3: Amount of current induced is directly proportional to ........................................

Table 4: Observation for amount of current induced current number of turns of coil

S.N	Action	Observation	Remarks
1	Magnet moved in coil of less turn	Deflection is ......... unit	.........(more/less) current is induced
2	Magnet moved in coil of more turns	Deflection is .......unit	........(more/less) current is induced

Result 4: ........................................

CONCLUSION

The above experiment on simulation proves Faraday law of electomagnetic induction. Which can be concluded in following points:

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4

Meiosis

Meiosis Cell Division

Prophase-I occurs over a long duration and involves several complicated changes in meiotic cell division. It is important because genetic recombination and variation in sexually reproducing organism occurs due to the events of this phase.
Leptotene
(i) The chromatin network opens out and threads become clear.
(ii) The chromosomes are thin, slender and long.
(iii) Chromosome number is diploid.

Zygotene
(i) Corresponding chromosomes become intimately associated.
(ii) The process of pairing is known as synapse. It is so exact that pairing is not merely between corresponding chromosomes but between corresponding individual units.
(iii) The chromosomes become shorter and thicker.

Pachytene or Pachynema
(i) The synaptic chromosomes become very intimately associated.
(ii) The pair of chromosomes becomes short and thick.
(iii) Crossing over occurs at this stage. Chiasmata are clearly seen. 

Diplotene
(i) Homologous chromosomes start separating from one another.
(ii) Chiasmata tend to slip out of the chromosomes. This is known as terminalisation of chiasmata.
(iii) Chromosomes start separating out but the separation is not complete.
(iv) Nuclear membrane and nucleolus start disappearing. 

Diakinesis
(i) The bivalents condense further and get randomly distributed.
(ii) The separation of paired chromosomes is almost complete.
(iii) Terminalisation of chiasmata is almost complete.
(iv) Nuclear membrane and nucleolus disappear. 

Interference_Bsc

English Listining Nine

 Welcome, You will find here the study materials of class 9

English

Chapter 1

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Chapter 6

Chapter 7

Chapter 8

Chapter 9

Chapter 10

Chapter 11

Chapter 12

Chapter 13

Chapter 14

Chapter 15

Chapter 16

Chapter 17

Chapter 18

 Optional Science Book Janak Publication

Aberration

Wave Nature of Light

aNature of LightOptics is a branch of physics which deals with study of phenomena like reflection, refraction, dispersion, interference, diffraction etc.This note provides us an information on nature and sources of light. Nature and Sources of LightOptics is a branch of physics which deals with study of phenomena like reflection, refraction, dispersion, interference, diffraction etc. The subject of optics has been divided into ray optics and wave optics. The branch of optics that deals with the production, emission and propagation of light, its nature and the study of the phenomenon of interference, diffraction and polarization is called wave optics.Nature and Sources of LightScientists have made discussion on true nature of light and have postulated various theories. These are discussed below: Newton’s Corpuscular TheoryNewton's theory of corpuscles, which are tiny particles shot out by luminous objects, states that they travel in straight lines and bounce off or pass into an object striking on it. However, this theory cannot explain interference, diffraction and polarization of light, making it incomplete and inaccurate.Huygens’ Wave TheoryAccording to this theory, light propagates from the source in the form of a wave. For the propagation of wave a medium is necessary. So, it was assumed that space is filled with medium called ether, which has the property of both elasticity and inertia. This theory says that light wave is longitudinal but actually light wave is transverse.Electromagnetic TheoryTheoretically light gets propagated in the form of electromagnetic waves, consisting of electric and magnetic fields mutually perpendicular as well as transverse to the direction of propagation of light. The electromagnetic waves propagate in free space with the velocity of light. Hertz demonstrated experimentally that electromagnetic waves propagate with velocity equal to that of light.Quantum Theoryin 1905 AD Einstein proposed a new theory of light called a quantum theory, in order to explain the photoelectric effect. According to this theory, light is transmitted as tiny packets of energy called photons and energy of each photon is given by E=hfwhere f is the frequency of light and h is Planck’s constant.Duel Nature of LightLight can exist in both particle and wave form. Using quantum theory, we can explain photoelectric effect. But this theory could not explain interference, diffraction and polarization. These phenomena can be explained using wave theory but wave theory could not explain photoelectric effect. Wave front According to wave theory, a source of light sends out disturbance or waves in all directions. A wave front as the locus of all adjacent points at which the phase of vibrations of a physical quantity associated with the wave is the same.

Types of Wave frontDepending on the nature of the source of light, there are three types of wave fronts:

Spherical Wave frontIt is produced by the point source of light. This is all because such points which are equidistant from the point source will lie on a sphere. A spherical wave front is shown in figure.Cylindrical Wave frontWhen the source of light is linear in shape (e.g a slit), all points equidistant from the linear source lie on the surface of a cylinder. Such a wave front is called a cylindrical wave front as shown in the figure.Plane Wave frontA small portion of cylindrical wave front or spherical wave front originating from a distant source will appear a plane and hence termed as plane wave front. Huygens‘ PrincipleHuygens ’ Principle enables us to determine what its position will be at some later time. In other words, the principle gives a method to know as to how light spread out in the medium. A source of light sends out wave front is propagated forwards through a homogeneous isotropic medium, Christian Huygens made the following assumptions. 1. Each point on a wave front acts as a new source of the disturbance. The disturbances from these points are secondary wave lets. These wavelets spread out in all directions in the medium with the velocity of light.2. The new wave front is then obtained by constructing a tangential plane to all the secondary wavelets. The new wave front is the envelope of to secondary wavelets at that instant.Laws of Reflection on the Basis of Wave TheoryConclusion of laws of reflection on the basis of wave theory:1. The angle of reflection r$r$ is equal to the angle of incidence i for all wavelengths and for any pairs of materials.r=i$$r=i$$2. The incident ray, reflected ray and normal to the reflecting surface all lie on the same plane.

If you look at the figure, AA’ is the wavefront incident on a reflecting surface XY having an angle of incidence i. Following Huygen’s principle, every point on AA’ will act as a source of secondary wavelets. Time taken from A’ to D = time taken from B’ to C A’D / v = B’C / v A’D = B’C A’C sin(i) = A’C sin(r) Thus, i = r Hence, the angle of incidence and angle of reflection are both equal. This is also stated by the first law of reflection. Additionally, as the incident wavefront AB, the normal and reflected wavefront are on the same plane, we can also verify the second law of reflection.Laws of Refraction on the Basis of Wave Theory

Let the angle of incidence be i$i$ and the refraction is r$r$.From the 𝛥A1B′B1$𝛥{\mathrm{A}}_1{\mathrm{B}}^{\prime }{\mathrm{B}}_1$, we getSin∠B′ A1B1=Sini≡B′B

AB1$\mathrm{S}\mathrm{i}\mathrm{n}\angle B^{\prime }{A}_{1}B1=\mathrm{S}\mathrm{i}\mathrm{n}\mathrm{i}\equiv \frac{B^{\prime }B}{A{B}_1}$From the △A1CB1$△{\mathrm{A}}_1\mathrm{C}{\mathrm{B}}_1$, we getSin∠A1B1C=Sinr=A1C

AB1$\mathrm{S}\mathrm{i}\mathrm{n}\angle A_{1}B1C=\mathrm{S}\mathrm{i}\mathrm{n}r=\frac{A_{1}C}{A{B}_1}$aThus Sini

Sinr=B′B

A1C$\begin{array}{l}Thus\\ \frac{\mathrm{S}\mathrm{i}\mathrm{n}i}{\mathrm{S}\mathrm{i}\mathrm{n}r}=\frac{B^{\prime }B}{A_{1}C}\end{array}$ =v1t

v2t$=\frac{{\mathrm{v}}_1\mathrm{t}}{{\mathrm{v}}_2\mathrm{t}}$or, Sini

Sinr=v1

v2=1 𝜇2$\frac{\mathrm{S}\mathrm{i}\mathrm{n}i}{\mathrm{S}\mathrm{i}\mathrm{n}r}=\frac{{\mathrm{v}}_1}{{\mathrm{v}}_2}{=}^1{𝜇}_2$ (constant)This proves Snell's law of refraction. The constant 1𝜇2${}^1{𝜇}_2$ is called the refractive index of the second medium w.r.t the first medium. Questions: Discuss about merits and demerits of Huygens' theory. Ans: Merits of Huygens' wave theory of light 1. It gives satisfactory explanation for laws of reflection, refraction and double refraction.2. It also explains the theory of interference and diffraction. 3. It experimentally proved that velocity of light in rarer medium is greater than that in a denser medium. De-merits of Huygens wave theory1. It could not explain Compton Effect, photoelectric effect, Raman Effect, rectilinear propagation of light etc. 2. It could not explain properly the propagation of light through vacuum (as it assumes the presence of material medium i.e. ether for the propagation of light wave in the whole universe).3. This theory is silent about the backward envelop of secondary wavelets. NumericalThe velocity of light in air is 3 x 108 m/s Find the velocity and wavelength of sodium light (𝜆${\displaystyle 𝜆}$= 5893Å${\displaystyle Å}$) in glass of refractive index 1.658. Given, Velocity of light in air (c) = 3 x 108 m/s Wavelength in air ( 𝜆${\displaystyle 𝜆}$) = 5893Å${\displaystyle Å}$ Refractive index of glass (µ) = 1.658 Velocity of light in glass (vg) = ? Wavelength of light in glass (𝜆g${\displaystyle {𝜆}_g}$) = ? We know that, 𝜇 = c

vg${\displaystyle 𝜇=\frac{c}{v_g}}$ vg = c

𝜇${\displaystyle v_g=\frac{c}{𝜇}}$ vg = 3 ×108

1.658=1.809×108 m/s${\displaystyle v_g=\frac{3\times {10}^8}{1.658}=1.809\times {10}^{8}m/s}$ We know For air c= f ×𝜆${\displaystyle c=f\times 𝜆}$ f=c

𝜆=3×108

5893 ×10-10${\displaystyle f=\frac{c}{𝜆}=\frac{3\times {10}^8}{5893\times {10}^{-10}}}$When light travels from one medium to another, its frequency remains unchanged. So, We can use the following relation For glassvg= f ×𝜆g${\displaystyle v_g=f\times {𝜆}_g}$ 𝜆g = vg

f= 1.809×108×5893×10-10

3×108${\displaystyle {𝜆}_g=\frac{v_g}{f}=1.809\times {10}^8\times \frac{5893\times {10}^{-10}}{3\times {10}^8}}$ = 3554.28 Å${\displaystyle =3554.28Å}$