The correct option is (c).
Explanation
A rainbow is a natural spectrum produced by the dispersion of sunlight by tiny water droplets present in the atmosphere. This phenomenon results from a combination of refraction, dispersion, and internal reflection of light.Statement-wise Analysis:
- Statement 1 is Correct: A rainbow is typically observed after rainfall when water droplets remain suspended in the atmosphere. For a rainbow to be visible to an observer on the ground, the Sun must be low in the sky (specifically, at an altitude of less than 42°). If the Sun is higher than this angle, the rainbow forms below the horizon and is not visible.
- Statement 2 is Incorrect: A rainbow is not a straight band of white light. It appears as a circular arc (or a complete circle if viewed from a high altitude, such as an airplane). Furthermore, it is not white; it consists of a spectrum of colors (VIBGYOR) caused by the dispersion of white sunlight into its constituent wavelengths.
- Statement 3 is Correct: The geometry of rainbow formation dictates that the observer must be positioned between the Sun and the rain. Sunlight enters the droplets from behind the observer, undergoes internal reflection within the droplets, and is directed back toward the observer's eyes. Therefore, one can only see a rainbow when one's back is towards the Sun.
Key Takeaway: A rainbow is formed by the refraction, dispersion, and internal reflection of sunlight in water droplets and is visible only when the Sun is behind the observer and the water droplets are in front.