Using this information, the equation I = I 0 cos 2 θ can be used to solve for the needed angle. When the intensity is reduced by 90.0%, it is 10.0% or 0.100 times its original value. What angle is needed between the direction of polarized light and the axis of a polarizing filter to reduce its intensity by 90.0%? Strategy Calculating Intensity Reduction by a Polarizing Filter For EM waves, the direction of the electric field is analogous to the disturbances on the ropes.Įxample 1. However, a vertical slit blocks the horizontally polarized waves. If a vertical slit is placed on the first rope, the waves pass through.

Those in the other rope are in a horizontal plane and are horizontally polarized. The oscillations in one rope are in a vertical plane and are said to be vertically polarized. To examine this further, consider the transverse waves in the ropes shown in Figure 3. Thus we can think of the electric field arrows as showing the direction of polarization, as in Figure 2. For an EM wave, we define the direction of polarization to be the direction parallel to the electric field. (This is not the same type of polarization as that discussed for the separation of charges.) Waves having such a direction are said to be polarized. Polarization is the attribute that a wave’s oscillations have a definite direction relative to the direction of propagation of the wave. There are specific directions for the oscillations of the electric and magnetic fields. As noted earlier, EM waves are transverse waves consisting of varying electric and magnetic fields that oscillate perpendicular to the direction of propagation (see Figure 2). Light is one type of electromagnetic (EM) wave. The electric and magnetic fields are perpendicular to the direction of propagation. An EM wave, such as light, is a transverse wave.

Polarized light intensity equation