can we create measuring device using our observed properties of light?

Can we create measuring device using our observed properties of light?

What would we need to know to determine if our device was accurate?

How do we know our spring scales are accurate?

1 kg

How do we know spring scales are accurate?

1 kg 4 kg2 kg

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offset or “blank”

How do we know spring scales are accurate?

1 kg 4 kg2 kg

0 1 2 3 4 5 60.0

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SI Units and time

How do we know spring scales are accurate?

1 kg 4 kg2 kg

0 1 2 3 4 5 60.0

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2 kg

How do we know spring scales are accurate?

1 kg 4 kg2 kg

0 1 2 3 4 5 60.0

1.0

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How do we know spring scales are accurate?

1 kg 4 kg2 kg

0 1 2 3 4 5 60.0

1.0

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tch

(cm

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mass (kg)

How do we know spring scales are accurate?

1 kg 4 kg2 kg

0 1 2 3 4 5 60.0

1.0

2.0

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5.0

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7.0

8.0

stre

tch

(cm

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mass (kg)

How do we know spring scales are accurate?

1 kg 4 kg2 kg

0 1 2 3 4 5 60.0

1.0

2.0

3.0

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5.0

6.0

7.0

8.0

stre

tch

(cm

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mass (kg)

How do we know spring scales are accurate?

0 1 2 3 4 5 60.0

1.0

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Calibration curve

What mass causes a stretch of 5.5 cm?

=4.34 kgFinal calibration dataStretch = mass (1.13) + 0.60Mass = (stretch – 0.60) / 1.135.5 cm

What would we need to know to make an accurate calibration curve for our

device?

Tank of milk and water

light sensor

Let’s look at milk fat globules in water

+using serial dilutions

0.2 mm diameter FOV

Homogenized milk contains many small globules of fat

Each mL of 2% milk contains about 10 million globules

…this “population density” is about 1010 globules/L

Visible light is scattered nicely by these globules, about 5 m across on average

Why milk?

About 10 m diameter glob is a big one

ten billion

Which is the size of many exxtremophile microbes we’ll be looking for .

The intensity of light that is transmitted decreases when the

milk fat density. . .

(millions of globules per liter)

(photoresistorvoltage) What will the

graph look like?

…what would our measurements be?

Will the calibration curve be similar for a smaller device utilizing the

same properties of light?• Insert picture & explanation of handheld

spec here