Which of the following statements regarding insolation is/are correct? 1. Insolation is predominantly shortwave radiation, with wavelengths in the range of 0.39 micrometre to 0.76 micrometre. 2. Insolation is evenly distributed across the Earth because of the Earth's curved surface. Select the correct answer using the code given below.

Insolation, or incoming solar radiation, is predominantly received in the form of shortwave radiation [3]. This includes ultraviolet and visible light, with the visible spectrum specifically ranging from approximately 0.39 to 0.76 micrometres [4]. Statement 1 is therefore correct as it accurately describes the wavelength range of the primary energy received. Statement 2 is incorrect because insolation is not evenly distributed across the Earth. Due to the Earth's geoid shape and curved surface, the sun's rays fall at varying angles of incidence, being more direct at the equator and oblique at the poles [3]. This results in significant latitudinal variation, with tropical regions receiving much higher energy (about 320 Watt/m2) compared to polar regions (about 70 Watt/m2) [2]. Factors like cloud cover and land-sea distribution further contribute to this uneven distribution [2].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > Insolation > p. 282
2. [3] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > SOLAR RADIATION > p. 67
3. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > 21.5. Heat Budget > p. 293
4. [2] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Spatial Distribution of Insolation at the Earth's Surface > p. 68