Question

ty uses a sailboat in a shadow play. when the sailboat moves closer to the screen, the shadow changes. the shadow represented by △abc changes to form △abc. what happens to the shadow? choose all that apply. it changes position. its vertices move along the rays. it changes size. it changes shape.

Explanation:

Step1: Analyze position change

When the sailboat moves, the shadow (triangle) moves on the screen. So, it changes position.

Step2: Analyze vertex movement

From the figure, we can see that the vertices of the triangle (shadow) move along the rays (the dotted lines representing the light paths).

Step3: Analyze size change

The original triangle \( \triangle ABC\) and the new triangle \( \triangle A'B'C'\) are similar (by the property of similar triangles formed by parallel - ray projection, like in shadow play where light rays are assumed parallel in a simple model). But their side - lengths are different (\(A'B'\gt AB\), \(B'C'\gt BC\), \(A'C'\gt AC\)). So, the size changes.

Step4: Analyze shape change

Since the triangles are similar (corresponding angles are equal as the rays are parallel and the projection is uniform), the shape does not change.

Answer:

It changes position, Its vertices move along the rays, It changes size.