The correct option is (a) 1 only.
Explanation
The phenomenon of seasons on Earth is primarily caused by two factors: the revolution of the Earth around the Sun and the tilt of the Earth's axis of rotation relative to its orbital plane. These factors determine the intensity and duration of insolation received at different latitudes throughout the year.
Statement-wise Analysis:
- Statement 1 is Correct: Seasons change because the Earth revolves around the Sun. As the Earth moves along its orbit, its position relative to the Sun changes. This revolution, combined with the axial tilt, results in the apparent movement of the Sun between the Tropic of Cancer and the Tropic of Capricorn, causing seasonal variations in temperature and daylight.
- Statement 2 is Incorrect: The Earth's axis is tilted at an angle of 66½° to the plane of its orbit (or 23½° from the vertical). Crucially, the axis maintains a fixed orientation in space as the Earth revolves around the Sun. This property is known as the parallelism of the Earth's axis. The axis always points towards the Pole Star (Polaris) and does not change its direction of inclination every six months. If the axis changed direction, the seasonal patterns would be erratic or non-existent.
Key Takeaway:
Seasons are the result of the Earth's revolution around the Sun combined with the constant tilt (parallelism) of its axis. The axis does not wobble or change direction during the annual cycle.