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Obtain the de Broglie wavelength associated with thermal neutrons at room temperature (27 °C). Hence explain why a fast neutron beam needs to be thermalised with the environment before it can be used for neutron diffraction

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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An electron microscope uses electrons accelerated by a voltage of 50 kV. Determine the de Broglie wavelength associated with the electrons. If other factors (such as numerical aperture, etc.) are taken to be roughly the same, how does the resolving power of an electron microscope compare with that of an optical microscope which uses yellow

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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The wavelength of a probe is roughly a measure of the size of a structure that it can probe in some detail. The quark structure of protons and neutrons appears at the minute length-scale of 10–15 m or less. This structure was first probed in early 1970’s using high energy electron beams produced by a linear accelerator at Stanford, USA. Guess what might have been the order of energy of these electron beams. (Rest mass energy of electron = 0.511

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Find the typical de Broglie wavelength associated with a He atom in helium gas at room temperature (27 °C) and 1 atm pressure; and compare it with the mean separation between two atoms under these

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Compute the typical de Broglie wavelength of an electron in a metal at 27 °C and compare it with the mean separation between two electrons in a metal which is given to be about 2 × 10–10 m. [Note: Exercises 35 and 36 reveal that while the wave-packets associated with gaseous molecules under ordinary conditions are non-overlapping, the electron wave-packets in a metal strongly overlap with one another. This suggests that whereas molecules in an ordinary gas can be distinguished apart, electrons in a metal cannot be distintguished apart from one another. This indistinguishibility has many fundamental implications which you

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(1) The electric field `vecE` due to a point change at any point near to it is defined as: `vecE=Lim vecF/q`where q is the test charge and `vecF` is the force acting on it. What is the significance of lim `qtoo` in this expression?(2) Two charges each `2 xx 10^(-7)` C but opposite in sign forms a system. These charges are located at points A (0,0, -10) cm and B(0,0, +10) cm respectively. What is the total charge and electric dipole moment of the

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(a) Sketch electric lines of force due to (i) isolated positive change (ie q>0) and(ii) isolated negative change ( ie q(b) Two point changes q and –q are placed at a distance 2a apart. Calculate the electric field at a point P situated at a distance r along the perpendicular bisector of the line joining the charges. What is the field when r >>

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(a) What is an equi-potential surface? Show that the electric field is always directed perpendicular to an equi-potential surface. (b) Derive an expression for the potential at a point along the axial line of a short electric

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(a) Define dielectric constant in terms of the capacitance of a capacitor? On what factor does the capacitance of a parallel plate capacitor with dielectric depend?(b) Find the ratio of the potential differences that must be applied across the(1) parallel(2) Series combination of two identical capacitors so that the energy stored in the two cases becomes the

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(a) An air filled capacitor is given a charge of 2 µ C raising its potential to 200 V. If on inserting a dielectric medium, its potential falls to 50 V, what is the dielectric constant of the medium?(b) A conducting stab of thickness‘t’ is introduced without touching between the plates of a parallel plate capacitor separated by a distance d (t < d). Derive an expression for the capacitance of a

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Figure (a) and (b) shows the field lines of a single positive and negative changes respectively(a) Give the signs of the potential difference : `Vp -Vq and V_B - V_A`(b) Give the sign of the work done by the field in moving a small positive change from Q to P.(c) Give the sign of the work done by the field in moving a small negative change from B to

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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With the help of a labelled diagram, explain the principle, construction and working of a vandegraff generator. Mention its

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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A block having mass `m = 4 kg` and charge `q=50 muC` is connected to a spring having a force constant `k=100 N'/'m`. The block lies on a frictionless horizontal track and a uniform electric field `E=5×10^5` V/m acts on the system as shwon in figure. The block is released from rest when the spring is unstretched (at `x = 0`) (a) By what maximum amount does the spring expand? (b) What is the equilibrium position of the block? (c) Show that the block's motion is simple harmonic and determine the amplitude and time period of the

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Two conducting plates A and B are placed parallel to each other. A is given a charge `Q_1 and B` a charge `Q_2` . Prove that the charges on the inner facing surfaces are of equal magnitude and opposite sign. Also find the charges on inner & outer

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Define these for a body in SHM

asked Mar 20, 2022 in 11th Physics by varun (6.7k points)

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What is Simple pendulum? Find an expression for the time period and frequency of a simple

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Velocity time graph of a moving particle is shown. Find the displacement (1) 0 – 4 s (2) 0 – 8 s(3) 0 - 12 s from the graph. Also write the differences between distance and displacement. [1 unit on Y axis is 1m; 1 unit on X axis is

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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(a) What is the angle between `vecA and vecB` if `vecA and vecB` denote the adjacent sides of a parallelogram drawn form a point and the area of the parallelogram is `1/2 AB` ?(b) State and prove triangular law of vector

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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(a) Define impulse. State its S.I. unit? (b) State and prove impulse momentum

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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(a) Define potential energy. Give examples.(b) Draw a graph showing variation of potential energy, kinetic energy and thetotal energy of a body freely falling on earth from a height

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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