A scanning tunneling microscope is used to measure small changes in height of a surface by detecting changes in the tunneling current between the tip and the surface. The current is proportional to the tunneling coefficient (ie. I = const * T) which follows the general equation for tunneling through a square well , with C dependent on the molecule and L is the distance. The transmission coefficient at one point is T = 0.01, what is the relative current if the distance is increased from L to 5L? We are interested in I(5L)/I(L). (Note: there may be more information provided than you need to solve the problem.)

Respuesta :

Answer:

[tex]\mathbf{\dfrac{I(5l)}{I(l) } =10^{-8}}[/tex]

Explanation:

We are being told that the current is proportional to the tunneling coefficient[tex]I(l) = I_0 e^{-2kl}[/tex] ;

where l = distance between the tip and the surface.

Let      [tex]I(l) = I_0 e^{-2kl}[/tex]        ------------  equation (1)

and     [tex]I(5l) = I_0 e^{-2k(5l)}[/tex]   ------------ equation (2)

Dividing equation (2) by (1); we have :

[tex]\dfrac{I(5l)}{I(l) } = \dfrac{I_0 e^{-2k(5l)}}{ I_0 e^{-2kl}}[/tex]

[tex]\dfrac{I(5l)}{I(l) } =e^{-2k(5-1)l}[/tex]

[tex]\dfrac{I(5l)}{I(l) } =(e^{-2kl})^4[/tex]

where ;

[tex](e^{-2kl})[/tex] represents the transmission coefficient T = 0.01

Thus; replacing the value for 0.01;we have;

[tex]\dfrac{I(5l)}{I(l) } =0.01^4[/tex]

[tex]\mathbf{\dfrac{I(5l)}{I(l) } =10^{-8}}[/tex]