Reddish Appearance of The Sun at Sunrise and Sunset

Introduction

One of the important phenomena in our daily life is light Scattering. This occurrence, like the blue color of the sky, the reddish appearance of the sun at sunrise and sunset, the color of the rainbow, and so on, has been observed by everyone since childhood. Light Scattering differs from light reflection and refraction in a significant way. The light beam gets reflected in a straight path, but the light ray gets scattered in diverse directions by the medium through which it passes. When a ray of light passes through a medium, it collides with the present particles. As a result, some photons get absorbed while others get spread or scattered in all directions.

Have you ever noticed how there occurs a reddish appearance of the sun at sunrise and sunset? You can witness a blue sky for the entire day, but before sunrise or sunset, the sky turns red or in some orangish hue. This happens due to a spectacular feature of light caused by its Scattering that causes this phenomenon. Light Scattering occurs when light rays collide with an obstruction such as dust, gas molecules, or water vapor and divert from their straight course. Let us study the phenomenon of Scattering of light in detail.

State Refraction

Refraction is the shift in a wave traveling through one medium to another. Light refraction is a well-known phenomenon, but other waves can also refract, such as sound and water waves. Because of refraction, we can even use optical equipment like magnifying glasses, lenses, and prisms. We can focus light on our retina thanks to light refraction.

State Atmospheric Refraction

Different layers of air make up the earth’s atmosphere. Some of these layers of the air have low densities and are hot, while others have high densities and are chilly. The optically rarer medium for light rays is the hot layers of air, whereas the optically denser medium for rays of light is the cold layers of air. As a result, when light rays are emitted by an object in the atmosphere, they pass through several layers of air with different densities and are refracted by the atmosphere.

Examples of Atmospheric Refraction

Star position: The refraction of starlight in the atmosphere causes the apparent star position. Varying layers of the atmosphere have different temperatures and densities. As a result, we have access to a diverse selection of media. A distant star is employed as a light source. As starlight enters the earth’s atmosphere, it is constantly refracted and bends towards the normal as its refractive index changes from rare to thick. As a result, the star’s apparent location differs from its true position. The star appears to be much bigger than it is. 

Twinkling of Star: Atmospheric refraction is partly a reason for this phenomenon. A single point of light emanates from a distant star. When the beam of starlight deviates from its route due to the physical condition of the earth’s atmosphere, the apparent position of the star changes. As a result, the amount of light entering our eyes varies, becoming brighter. This is why it is also called the ” Star Twinkling Effect.”

Scattering of Light

When light flows through a material that contains obstructions floating in it, it scatters. For example, sunlight is scattered by atoms, molecules, dust particles, water droplets, and other obstacles in the atmosphere before reaching the earth’s surface, which is responsible for various natural phenomena such as the blue color of the sky, the reddish color of the sun during sunrise and sunset, and so on. The molecules absorb the incident light and then re-radiate in diverse directions in the Scattering of light phenomena. When light encounters barriers in the medium through which it travels, the direction of light alters owing to dispersion.

Name the Types of Scattering of Light

The energy of the scattered light can be used to classify light scattering. They are as follows:

• Elastic Scattering: This type of Scattering occurs when the energy of the scattered light is conserved
• Inelastic Scattering: When the energy of dispersed light is not preserved, it is referred to as inelastic Scattering

Factors Affecting Light Scattering

• Size of the particles: The colour of scattered light is determined by particle size
• Wavelength: Light with a shorter wavelength is scattered by tiny particles

Large particles disperse longer wavelength light.

The ray’s wavelength: Scattering is inversely proportional to the ray’s wavelength. The lower the Scattering, the higher the wavelength. The higher the Scattering, the shorter the wavelength. The reddish appearance of the sun at sunrise and sunset is due to this phenomenon because the rays are so close to the horizon that they must travel a greater distance through the atmosphere. As a result, light that isn’t red is primarily scattered. Our eyes receive the majority of the red light, which is the least dispersed. As a result, the sun and the sky appear to be crimson.

Examples of Scattering of Light

Blue sky colour: The Rayleigh scattering of sunlight is responsible for the sky’s blue colour. The visible light from the sun has a wavelength that ranges from 400 nanometers for blue to 800 nanometers for red. The molecules scatter the light from the sun in the atmosphere as it travels through the atmosphere. Because the size of the molecules scattering light from the sun is 10-10m, which is much smaller than the wavelength of the incident light, Rayleigh Scattering holds, and the intensity of the scattered light varies inversely as the fourth power of the wavelength of light. Because the wavelength of blue light is almost half that of red light, the intensity of scattered blue light is approximately 24 times that of the red light that causes. As a result, blue prevails, and the sky is seen.

At sunrise and sunset, the sun seems to be reddish: To answer the query of why the sun appears reddish at sunrise and sunset, The sun is near the horizon during sunrise and sunset. To reach the observer, the sun’s rays must travel a greater distance through the dense section of the atmosphere. The majority of the blue light is scattered away along with the travel of the light rays. The colour red, which has the longest wavelength of all the colours in the visible spectrum, is the least dispersed. As a result, the light from the sun during sunrise and sunset that reaches the observer’s eye consists primarily of light with longer wavelengths, such as red. As a result, the sun appears reddish at sunrise and dusk.

The colour red indicates danger: Red has the longest wavelength of all the visible light colours. When light travels through the atmosphere, it is scattered by the atoms and molecules that make up the atmosphere. Rayleigh scattering is legitimate because the size of these atoms or molecules is substantially less than the wavelength of the incident light. The red colour is the least scattered because the intensity of scattered light correlates inversely with the fourth power of wavelength, which is also responsible for causing the reddish appearance of the sun at sunrise and sunset. As a result, the red color may be seen from a great distance. Even when there is fog or the environment is not particularly clean, the red color may be seen. That is why the color red is used to indicate danger.

Conclusion 

We discovered that light Scattering is the phenomenon of incident light changing direction after colliding with objects in the medium through which it is traveling. In this article, we learned why light with a longer wavelength, such as red, scatters the least and light with a shorter wavelength, such as blue, scatters the most.

As a result, light scattering is responsible for various visual phenomena, including the blue color of the sky. During the day, the reddish appearance of the sun at sunrise and sunset, and others, some of which have been discussed in the article. Overall, we hope that this article has piqued your interest in learning more about the phenomenon of light scattering.