Polarization of Electromagnetic Waves Quiz Quiz

Explore key principles of electromagnetic wave polarization, including types, mechanisms, real-world effects, and fundamental behaviors. This quiz evaluates your understanding of polarization phenomena, properties, and related terminology essential for physics and engineering studies.

1. Identifying Types of Polarization

   When electromagnetic waves vibrate in a single fixed plane as they travel, which type of polarization is being exhibited?

   1. Random polarization
   2. Circular polarization
   3. Elliptical polarization
   4. Linear polarization

   Explanation: Linear polarization occurs when the electric field of an electromagnetic wave oscillates consistently in one direction. Elliptical polarization involves the tip of the electric field tracing an ellipse, and circular polarization is a special case where it traces a circle. Random polarization is not a standard classification and typically refers to unpolarized light where polarization direction varies randomly.

2. Polarization by Reflection

   At a specific angle known as Brewster’s angle, reflected light becomes completely polarized when striking a non-metallic surface. Which component of the electric field is present in the reflected wave at this angle?

   1. Parallel to the plane of incidence
   2. No electric field component
   3. Perpendicular to the plane of incidence
   4. Both perpendicular and parallel components

   Explanation: At Brewster’s angle, the reflected light’s electric field is perpendicular to the plane of incidence, making it linearly polarized. The parallel component is eliminated because it is transmitted into the medium rather than reflected. Having both components or no electric field is incorrect; polarization means only the perpendicular remains in reflection at this angle.

3. Effect of a Polaroid Filter

   If unpolarized light passes through an ideal polarizing filter (Polaroid) whose axis is vertical, what is the expected intensity of the transmitted light compared to the original?

   1. Half the original intensity
   2. The same as the original intensity
   3. One quarter of the original intensity
   4. Zero intensity

   Explanation: A polaroid transmits only the component of the electric field aligned with its axis. For unpolarized light, this means exactly half of the original intensity passes through. Saying one quarter is incorrect—this would apply only after passing through a second perpendicular filter. Transmitting the same intensity or zero intensity is also false for ideal polarizers.

4. Circular Polarization Scenario

   Which condition must be true for an electromagnetic wave to be circularly polarized?

   1. Randomly oriented electric field vectors
   2. Two perpendicular electric fields of unequal amplitude with a 45-degree phase difference
   3. A single electric field component with constant direction
   4. Two perpendicular electric fields of equal amplitude with a 90-degree phase difference

   Explanation: Circular polarization requires two perpendicular electric field components that are equal in magnitude and have a phase difference of exactly ninety degrees. A single component keeps the wave linearly polarized. Unequal amplitudes or a different phase difference create elliptical polarization, and random orientations do not result in polarization.

5. Malus’s Law Application

   According to Malus's Law, what happens to the intensity of polarized light when it passes through a second polarizer at an angle θ to the original polarization direction?

   1. Intensity remains unchanged
   2. Intensity becomes zero for all θ except 90 degrees
   3. Intensity is multiplied by cos²θ
   4. Intensity is multiplied by sinθ

   Explanation: Malus’s Law states that the transmitted intensity through a second polarizer is the original intensity times the square of the cosine of the angle between polarization axes. The intensity does not remain unchanged unless θ is zero. Using sinθ is incorrect; the law uses the cosine function. The intensity only becomes zero when θ is 90 degrees, not all other angles.