mountain ridge, mountain peak
岭 centers on a mountain ridge or peak: a high, narrow crest along a mountain.
岭 combines 山 (mountain) with 令, which likely contributes the sound. The character is used for mountain ridge or peak.
The left side 山 is a mountain, and the right side 令 looks like a person standing on a peak giving a command. Picture a mountain ridge where a leader stands and points out the peak.
For レイ, imagine a ray of sunlight hitting the mountain ridge at dawn: ray -> レイ, and the light outlines the peak.