Passage I
The LCD screen of a laptop computer emitted plane-polarized light. (A plane-polarized light wave always vibrates along the same axis [for example, up and down]). A special filter was placed in front of the computer screen. Light from the screen passed through the filter and struck a light sensor that was attached to a voltmeter, producing a voltage, V (see Figure 1). As the angular position, θ, of the filter varied, V varied.
A graph of V, in volts, versus θ, in degrees, is shown in Figure 2. Figure 3 shows the relationship between V and the filtered light's intensity, I, in lux.
3. Based on Figures 2 and 3, for which of the following values of θ would I be closest to 18 lux?
Your Answer is
Correct Answer is B
Explanation
Look at figure 3 first, when the ordinate I=18, the abscissa V=3.6;
Look at figure 2 again, when the ordinate V=3.6, the abscissa θ=70°