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University of Wisconsin - Milwaukee

# An interferometer is used to measure the length of a bacterium. The wavelength of the light used is 650. nm. As one arm of the interferometer is moved from one end of the cell to the other, 310. fringe shifts are counted. How long is the bacterium?

## 50.4 \mu m

#### Topics

Electromagnetic Waves

Wave Optics

### Discussion

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##### Christina K.

Rutgers, The State University of New Jersey

##### Aspen F.

University of Sheffield

### Video Transcript

So here we're trying to find the length of the bacterium using an interferometer. So the web link of the light used is 650. Narrator The total friendship while moving the arm from one end of the bacterium to the other end is 310 fringes. Now, using the fact that Lambda by Ford instance moved is equal to one friend shift just like the problems we did before we can write down and equals Delta L over, they'll lambda before. Okay, remember, Delta is the total distance move by the arm, and in this case, actually, that is going to be the size of the bacteria. So I'm gonna write down Delta L. It calls size off the bacterium. So from here, still to l is going to be and times Lambda over four. And that's going to be 3 10 times 6 50 times 10 to the negative nine over for, And this is going to give me 5.4 times 10 to the negative five meter, which is 50 points for micrometer

University of Wisconsin - Milwaukee

#### Topics

Electromagnetic Waves

Wave Optics

##### Christina K.

Rutgers, The State University of New Jersey

##### Aspen F.

University of Sheffield