光 and 影: light and shadows
Distinguish light from a shadow and an actual object from its projected outline.
Movement of light
光, read ひかり, means light. 窓から光が入ってきます。 says that light comes in through the window.
光の向きを変えました。 means changing the direction of the light. It does not report changing its color or brightness.
A shadow's location
影, read かげ, here means shadow. 壁に人の影が映っています。 says that a person's shadow appears on the wall.
木の影が長くなりました。 says that the tree's shadow became longer. It does not say that the tree itself grew.
Shadow and actual person
影だけ見えて、本人は見えませんでした。 says that only the shadow was visible, not the person. Do not add seeing the person's face.
光が弱くなると、影が見えにくくなりました。 says that as the light weakened, the shadow became harder to see. 見えにくい describes difficulty seeing, not complete absence.
Does 木の影が長くなりました mean that the tree grew?
Show the answer and why
No. What became longer was the tree's shadow.