Question

Just after sunrise, you look straight up at the sky. Is the light you see polarized? If so, in what direction?

Short answer

If so, what is the direction of polarization? Answer: Yes, the sunlight seen when looking straight up at the sky just after sunrise is polarized. The direction of polarization is horizontal.

Step-by-step solution

Understand the situation

The situation describes looking straight up at the sky just after sunrise. This means that the sunlight is shining from close to the horizon while the observer is looking directly overhead (90° from the horizon).

Recall the relationship between polarization and scattering

Polarization of light occurs when light waves vibrate in a particular direction. In the atmosphere, the scattering of sunlight by particles in the atmosphere (e.g., gas molecules, dust, and aerosols) can cause polarization. Rayleigh scattering is responsible for the polarization of sunlight, where shorter wavelengths are scattered more than longer wavelengths causing the sky to appear blue.

Identify the condition for maximum polarization at 90-degree scattering angle

Maximum polarization of the scattered light occurs when the observer is positioned at a 90-degree angle with respect to the incident sunlight. In our case where we are looking straight up, the angle between the observer and the sunlight is 90 degrees.

Determine the direction of polarization

When the scattering angle is 90 degrees, the direction of polarization is perpendicular to the plane formed by the sunlight and the observer's line of sight. In this case, since the observer is looking straight up at the 90-degree angle, the plane formed by the sunlight and the observer's line of sight is parallel to the horizon. Therefore, the direction of polarization will be horizontal. To summarize, the sunlight you see when looking straight up at the sky just after sunrise is polarized, and the direction of polarization is horizontal.