Calculate the value of the wavelength, Electrical Engineering

In an electron microscope, a beam of electrons is produced by a device called an electron gun. In the electron gun, electrons are 'boiled off' from a heated filament (which is the cathode and held at high negative voltage) and are attracted towards an anode. The high voltage difference ΔV causes the electrons to accelerate.

(i) Assuming that the speed of the electrons is zero as they are emitted from the filament and that as they reach the anode it is v, find an expression relating the final speed v to the charge on an electron, the mass of an electron and ΔV, and hence calculate the speed v of the electrons after passing through a voltage difference of 120 kV. You should identify clearly the three main steps in your answer ('Decide how you are going to tackle the problem'; 'Do the calculation'; 'Check that your answer makes sense') and you should state any assumptions that you make. You should show all of your working.

(ii) The wavelength, λ, of a beam of electrons is related to the speed, v, and mass, m, of the electrons by the following equation:

 λ, = h/mv

      where h is the Planck constant. Use this equation and your answer to part (i) to show that the wavelength λ of the electrons is related to the high voltage difference ΔV by the following equation:

λ2, = h2/2emΔV

(iii) Calculate the value of the wavelength of a beam of electrons in a microscope operated at 120 kV as in (i) and also at 15 kV. Your working should show explicitly how you arrived at units of length (metres) for your answers.

(iv) Compare the speed you calculated in part (i) with the speed of light and hence comment on the reasons why your calculated results may be inaccurate.

Posted Date: 2/23/2013 6:21:01 AM | Location : United States

Related Discussions:- Calculate the value of the wavelength, Assignment Help, Ask Question on Calculate the value of the wavelength, Get Answer, Expert's Help, Calculate the value of the wavelength Discussions

Write discussion on Calculate the value of the wavelength
Your posts are moderated
Related Questions
What are the advantages of distributing windings in an alternator?

Explain DAA instruction. DAA: The DAA instruction follows the instruction ADC or ADD to adjust the result in a BCD result. The DAA instruction performs only with the AL registe

Objective: To Understand the Usage of the Output ports of PIC18F452 and make changes in the previous code accordingly. Procedure: 1. Open the p1.asm program from t

Discuss all the five software interrupt instructions. The INTEL family microprocessor consist of software interrupts INT, INT0, INT3 and BOUND and IRET. Out of all these five

Series-Parallel Magnetic Circuit: Figure shows an electromagnet made of cast steel contain a coil of 500 turns wound on the central limb. The cross-sectional area of the outer

This assignment is to develop a User Requirements Specification for an electronic monitor and alarm system for an Oil Separator in Surface Water Drainage Systems. These separato

Q. Do the following operations with 8 bit bytes, and indicate the condition of the overflow and carry bits. a) 10111011 + 00000011 b) 11101101 + 11111001 c) 11011011 + 110

Q. The parameters of a BJT are given by α = 0.98, I CBO = 90 nA, and i C = 7.5 mA. Find β, iB, and iE.

Refer to the op amp circuit shown below. Let R 1 = 140 k_, R 2 = 10 k_, R 3 = 10 k_, R 4 = 20 k_, RL = 10 k_. Assume the op amp is ideal. Find the equation relating the

Q. A wye-connected, three-phase, 50-Hz, six-pole synchronous alternator develops a voltage of 1000 V rms between the lines when the rotor dc field current is 3A. If this alternator