Question

le tertre de départ d’un terrain de golf se trouve au bas d’une petite colline, comme le montre l’illustration ci - dessous. on y a installé un dispositif à deux miroirs plans qui agit à la manière d’un périscope : il permet au joueur, avant de frapper sa balle, de vérifier si l’allée est libre, en haut de la colline. tracez le trajet d’un rayon lumineux qui permet au golfeur de voir si l’allée est dégagée.
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illustration: dispositif à deux miroirs, allée, départ, et un golfeur au départ

Explanation:

To determine the light ray path in the periscope - like mirror system:

1. First, consider the light coming from the "Allée" (fairway) towards the upper mirror. The law of reflection (angle of incidence = angle of reflection, with the normal to the mirror surface) applies here. So, we draw a normal (perpendicular) to the upper mirror at the point where the light hits it. Then, the incident ray from the fairway and the reflected ray (towards the lower mirror) make equal angles with this normal.
2. Next, for the lower mirror, the light ray from the upper mirror hits it. Again, draw a normal to the lower mirror at the point of incidence. The incident ray (from the upper mirror) and the reflected ray (towards the golfer's eye) make equal angles with this normal.
3. The overall path starts from a point on the "Allée", reflects off the upper plane mirror, then reflects off the lower plane mirror, and finally reaches the golfer's eye at the "Départ" (start) area.

Answer:

1. Draw a ray coming from the "Allée" (fairway) towards the upper mirror. At the point of incidence on the upper mirror, draw the normal (perpendicular to the mirror). The incident ray and the reflected ray (towards the lower mirror) should make equal angles with this normal.
2. Then, for the lower mirror, draw the normal at the point where the ray from the upper mirror hits it. The incident ray (from upper mirror) and the reflected ray (towards the golfer) should make equal angles with this normal. The final reflected ray should be directed towards the golfer at the "Départ" area. (Since this is a drawing - based task, the answer is the described method to trace the light ray path using the law of reflection for plane mirrors.)