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The de Broglie wavelength is given by

$$\lambda\equiv\frac{h}{mv}$$

Now, if we have a small body, it's wavelength will be large when it is in motion. Similarly, a large body will have small wavelength. It can be seen from the equation. First of all tell me if I am right about these observations.

I was studying electron microscope and there was a sentence in it,

The fact that microscopic particles as the electron have extremely short de Broglie wavelengths has been put to practical use in many ultra modern devices.

It says that the electron, being a small particle, has a short de Broglie wavelength. But if we look at the equation, we see that small bodies will have large wavelength (provided that my observations about the equation are correct).

So my question is: why does a small particle as the electron has a small wavelength?

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    $\begingroup$ it is related to mass not the size of the particle $\endgroup$ – Dimensionless Aug 1 '13 at 4:17
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The statement:

"the fact that microscopic particles like electron have extremely short de-broglie wavelengths has been put to practical use in many ultra modern devices."

is talking of the wavelength, which does not only depend on rest mass( your m is the relativistic mass) :

wavelength dBroglie

The electron gets to relativistic velocity much faster than heavier particles, and that makes the difference to the wavelength, the gamma.

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