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
Based upon the following inputs, propose the optimal course of action for this venture: Probability of success: 30%; probability of failure: 30%; base case probability: 40%

You have been requested by your Senior Engineer to design a lift control unit (LCU) and prepare a report detailing your proposed solution. The client requires a microcontroller bas

Q. Explain working of Digital-to-Analog Converters? Digital-to-Analog (D/A) Converters For the results of digital computations to be used in the analog world, it becomes n

Briefly explain single mode and multimode fibres The optical fibres were categorized within two according to the number of modes it passes as: • Single mode fibres • Multi mode

Q. Consider the synchronous counter shown in Figure of the text. (a) Draw its timing diagram. (b) Show the implementation of the same synchronous counter using D flip-flops.

Diode Circuits: Prob. (a) Draw the piecewise linear volt ampere characteristic of a p n diode. What are the circuit models for the ON state and the OFF state. (b) Determ

Balanced Budget Laws: Laws (usually passed by right-wing governments) that require governments to run balanced budgets regardless of state of the overall economy. These lawshave th


Calculation of Aggregate Technical and Commercial Loss The concept of AT&C loss was introduced within 2001-02. The AT&C losses are presently in the range of 18% to 62% in seve

Hardware Requirement- Server of adequate sizing for enterprise-wide deployment for storing maps and geospatial data. Application server and web server. Desktops