Give reasons for the following: a) Red traffic signals can be seen from a very long distance. b) Stars appear to be slightly higher than their actual position.

a) Red traffic signals can be seen from a very long distance:
• The reason red traffic signals are visible from a long distance is because of the wavelength of the color red. Red light has a longer wavelength compared to other colors in the visible spectrum. Longer wavelengths can penetrate atmospheric particles and scatter less than shorter wavelengths. This phenomenon is known as Rayleigh scattering.

• In practical terms, red light is less likely to be scattered by dust, water droplets, and other particles in the atmosphere. This property allows red light to travel a longer distance with less attenuation, making red objects, including traffic signals, more visible from afar.

b) Stars appear to be slightly higher than their actual position:

• This phenomenon is known as stellar aberration and is a result of the Earth’s motion through space. As the Earth moves along its orbit around the Sun, it causes a change in the direction of starlight due to the combination of the Earth’s velocity and the finite speed of light.

• Stellar aberration causes stars to appear slightly displaced from their actual position in the sky. The effect is similar to raindrops hitting a moving car windshield. If the car is moving, raindrops will appear to come from a direction slightly in front of their actual path. Similarly, the motion of Earth causes starlight to be slightly shifted in the direction of the Earth’s orbital motion.

The angle of displacement is tiny, and it does not affect the overall appearance of the stars to the naked eye. However, precise measurements and observations by astronomers take this phenomenon into account to accurately determine the positions of celestial objects.