sunlight; solar rays
Refers to the light and rays emitted by the sun, often with a slightly scientific or descriptive tone.
Sunlight is streaming into the room.
I apply sunscreen to protect my skin from strong solar rays.
日光 is the common, everyday word for sunlight. 太陽光線 is more specific to the rays themselves and can sound more technical or descriptive.
太陽光 is often used in contexts like solar power generation (太陽光発電). 太陽光線 emphasizes the beams or rays of light.
Compound of 太陽 (sun) + 光線 (light rays, beam).