In this part of the experiment, make all measurements with the resistance of the variable resistor approximately equal to 3 kΩ. Write down the value of the resistance at which you have taken your measurements. Install the neutral filter on the optical bench between the laser and the photodetector. Turning the laser ring, make sure that the maximum voltage across the resistor is approximately 180-190 mV. Measure in the range of the multimeter 200mV. In this mode, the voltage on the multimeter is directly proportional to the intensity of the incident light. Hold the light filters with the clothes-peg and hold them directly near the photodetector.
The intensity of the light I transmitted through the filter is proportional to the intensity of the incident light I0:
I=kI0(1)
The transmittance k does not depend on the intensity of the incident light but may depend on its wavelength.
2.1 Using formula (1), obtain the dependence of the intensity of transmitted light through n identical light filters on the number n of light filters.
2.2 Measure the dependence of the light intensity I on the number of filters n for all the filters provided (gray, yellow and blue). Draw graphs of the dependencies obtained in scales that allow you to verify the formula obtained in Section 2.1.
2.3 Calculate the transmittance of all filters. Estimate the experimental errors of their values.
2.4 Measure the transmittance for pairs of different filters: gray + blue, gray + yellow; blue + yellow. Theoretically calculate the transmittance of each pair of filters.