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

Q. (a) Consider the amplifier block in the circuit configuration of Figure. Find an expression for v 2 /v 1 in terms of R i , R o , and A of the amplifier. (b) Determine the

How does a Mach-Zehnder Modulator work in Silicon?

LAN topologies: Network topology is a physical schematic that demonstrates interconnection of the many users. There are four fundamental topologies as under: (i) Direct Connect

Q. Show the procedure of Octal to Decimal Conversion? To convert from Octal to Decimal, multiply the value in every position by its Octal weight and add each value. Using the v

Q. The twin-tee or notch network shown in Figure is often used to obtain band-reject characteristics. (a) Determine the transfer function V 2 /I 1 . (b) Find the angular freq

Visual Presentation of an Electrical Network: The second layer corresponds to the distribution network coverage. The low voltage system and customer supply points along with l

Voltage  and Frequency Control Methods In this  control  method the ratio of voltage  to frequency is kept constant so that the  flux  remains  constant. The voltage  at varia

Metal Oxide Field Effect Transistor The metal-oxide-semiconductor field-effect transistor (MOSFET/MOS-FET/MOS FET) is a device employed for amplifying or for switching electr

Which Segment is used to store interrupt and subroutine return address registers? Ans) Stack Segment in segment register is used to kept interrupt and subroutine return address