Question

A student is examining a bacterium under the microscope. The E. coli bacterial cell has a mass of m = 0.100 fg (where a femtogram, fg, is 10−15g) and is swimming at a velocity of v = 4.00 μm/s , with an uncertainty in the velocity of 1.00 % . E. coli bacterial cells are around 1 μm ( 10−6 m) in length. The student is supposed to observe the bacterium and make a drawing. However, the student, having just learned about the Heisenberg uncertainty principle in physics class, complains that she cannot make the drawing. She claims that the uncertainty of the bacterium's position is greater than the microscope's viewing field, and the bacterium is thus impossible to locate. Part A What is the uncertainty of the position of the bacterium?

Answer 1

Heisenberg uncertainty principle states that we cannot know the position and momentum accuretly.

Mathematically it is represented as

------ equation 1

uncertainity in momentum

= Uncertainity in position

h = planks constant

= 6.626068 × 10^-34 m² kg / s

mass x 0.02 x 10^-6 m/s

= 0.100 x 10^-15 g x 0.02 x 10^-6 m/s

= 0.100 x 10^-18 kg x 0.02 x 10^-6 m/s

= 0.002 x 10^-24 kg m/s

From equation 1 we get that

= h/(2x)

= (6.626068 × 10^-34 m² kg / s)/2 x (x0.002 x 10^-24 kg m/s)

= 5.27 x 10^-10 m

The uncertainity in position is 5.27 x 10^-10 m