Question

The sky looks blue due to (a) dispersion effect (b) reflection (c) transmission (d) scattering

Short answer

The sky appears blue due to scattering.

Step-by-step solution

Understand the Principles of Light

Light from the sun appears white but is actually composed of various colors, as seen in a rainbow. Each color in the light spectrum has a different wavelength. Blue and violet light have the shortest wavelengths and are scattered in all directions more than any other color as sunlight passes through the atmosphere.

Rule out Incorrect Options

The phenomenon of sky looking blue is not due to to dispersion effect or transmission. Dispersion explains why we see a rainbow, not why the sky is blue. Transmission is when light travels from one medium to another without changing direction, which isn't applicable here.

Choose the Correct Option

The sky appears blue not because of reflection, but because of the scattering of sunlight by the atmosphere. The blue color of the sky is the result of a particular type of scattering called Rayleigh scattering. Therefore, the correct choice is (d) scattering.

Key concepts

Light Spectrum

The light spectrum is essentially the full range of light waves that we can see, also known as visible light. This spectrum includes all the colors that we see in the world around us. Each color corresponds to a different wavelength, with red having the longest wavelength and violet the shortest. When sunlight hits a prism, it splits into various colors forming a rainbow, which demonstrates the different wavelengths in the light spectrum. This concept is essential because it helps explain why different colors appear under various conditions, especially in our atmosphere.

Wavelength

Wavelength is an important term in understanding light. It refers to the distance between consecutive peaks of a wave. Light waves, like those from the sun, travel in this wave-like pattern. Different colors have different wavelengths:

• Red light has a longer wavelength.
• Blue and violet light have shorter wavelengths.

These differences in wavelength are crucial when studying phenomena like Rayleigh scattering, which affects how we perceive color in the sky.

Atmosphere

Our atmosphere is a layer of gases surrounding the Earth and plays a critical role in how we perceive light. As sunlight enters the atmosphere, it doesn't pass through unimpeded. Instead, it interacts with gases and particles in the air. This interaction is what causes certain light waves, or wavelengths, to scatter more than others. The thickness and composition of the atmosphere contribute to different scattering effects, which help explain changes in sky color throughout the day.

Color Scattering

The scattering of light, especially by particles much smaller than the wavelength of light, leads to interesting visual effects. Rayleigh scattering is the specific type of scattering responsible for the sky's blue color. It occurs because shorter wavelengths (blue and violet) scatter more than the longer wavelengths (red and yellow) due to their size relative to air particles:

• Shorter wavelengths (blue and violet) scatter more effectively in all directions.
• Longer wavelengths (like red) pass through the atmosphere more directly.

This selective scattering allows us to see a predominantly blue sky, as our eyes are more sensitive to blue light and because the violet light scatters in a way that blends with the surrounding light, enhancing the blue color we perceive.