Astronomy and Celestial Phenomena

Twilight is seen because the earth's atmosphere, some light scatters through small particles in the atmosphere- so, there is still some light n the sky even after the sun  has gone down.

Because the Earth is a sphere, the Sun can only illuminate one half of its surface at any given time, while the other half remains in darkness.

According to Wien's Displacement Law, the wavelength of peak emission is inversely proportional to the temperature. If the temperature increases, the peak wavelength shifts to a shorter value.

At the North Pole, the Sun rises at the spring equinox (March 21) and sets at the autumnal equinox (September 23), resulting in six months of daylight followed by six months of darkness.

Among the constituent colours of white light, red has the longest wavelength and hence least frequency. As a result, red is least scattered among all colours. So, red colour reaches our eyes while all other colours scatter away during sun-rise and sun-set.

Near the horizon sunlight passes through thicker layers of air having larger particles that scatter light of longer wavelength such as the red end of the spectrum. Also it travels larger distance at horizon before reaching the earth. However, light from the Sun overhead travels relatively shorter distance. At noon, the Sun appears white as only a little of the blue color is scattered whereas, near the horizon, most of the light of shorter wavelength at the blue end of the spectrum are scattered away by the small particles of the atmosphere. Therefore, the light that reaches our eyes is of longer wavelength which gives rise to the reddish appearance of the Sun.

C. The blue colour of sky is due to scattering of light   = correct statement

The blue colour of sky is due to the scattering of light by small particles of the atmosphere (air molecules) when the light is incident on particles whose size is smaller than the wavelength of light, it is scattered.

According to Rayleigh law, the intensity of scattered light is inversely proportional to the fourth power of wavelength.

Option C is correct answer.

During sunset and sunrise, the rays have to travel a larger part of the atmosphere because they are very close to the horizon. Therefore, light other than red is mostly scattered away. Most of the red light, which is the least scattered, enters our eyes. Hence, the sun appear red..

According to Rayleigh's law of scattering, amount of scattering $\alpha \frac {1}{\lambda^4}$.
Red having maximum wavelength straight to the observer.
Most of the scattered light goes towards the sky, so the sky appears blue.

Seasons are primarily caused by the tilt of the Earth's axis, which changes the angle of sunlight and the duration of daylight throughout the year as the Earth orbits the Sun.

The Earth reaches perihelion, its closest point to the sun, in early January. This is due to the Earth's elliptical orbit.

Guttation is the loss of water in liquid form as a dilute solution from uninjured leaf tips. The uninjured leaf tips have hydathodes or water stomata. Under conditions of low transpiration dilute solution of minerals oozes out through them under the influence of increased root pressure. Thus, mostly guttation is observed during night time when transpiration is low, for example, due to high atmospheric humidity and sufficient water is present in soil. The most important force responsible for guttation is positive root pressure.