Measuring the speed of light
Observation Observation



1. Move the movable mirror selecting either button Decrease distance s of reflector or button Increase distance s of reflactor. Watch through the camera, the train moving. Stop motion by pressing Stop train - measure distance s of reflactor. Check if the distance s given on the computer screen associated with that resulting from the image you see through the camera.

2. Observe the changes that occur in the two signals on the screen of the oscilloscope when the train is moving. I owe?

3. Can calculate the time Dt when the two pulses have different heights? For what reason?

Measuring the speed of light.

1. Move the mirror moving in any direction you want by pressing the appropriate key (see above).

2. Stop the mirror by pressing the appropriate button. Note the value of the distance s, in mm, shown on the screen below the button Stop train - measure distance s of reflactor.

3. With proper use of keys Open ---------- diaphragm for measurement signal ---------- Close and Open ---------- diaphragm for reference signal --- ------- Close, adjust the height of the two pulses to be equal to each other.

4. Pressing Oscilloscope screenshot, on the left side of the screen below the two pictures that show the cameras from the lab, a window pops up with the photo of the screen of the oscilloscope. Save this picture giving her name as the value distance s measured in the previous step.

5. Repeat steps 1-4 five times, each time choosing a different distance s.

6. What is the advantage of making multiple measurements instead of just one, to calculate the speed of light?

7. Given that the accuracy of the distance s is about 1 cm, what uncertainty enters into the measurement of the time interval Dt, and what is the corresponding uncertainty in the value of the speed of light?


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