Commonly-asked PSLE Light & Shadow Question

The shadow performance question has appeared in the PSLE Science paper twice in the recent years. The version below appeared in the 2019 paper.



In both versions of the question, the actors were all of the same height. That being the case, the only factor that affects the size of each shadow is the distance the actor is from the light source/screen.


To answer this question, students need to recall the following principles:

  • As the object moves closer to the light source or further away from the screen, the size of the shadow increases.

  • As the object moves further from the light source or closer to the screen, the size of the shadow decreases.

It is worth reminding students that as the distance of the object from the light source/screen varies, the size of the shadow varies both in height and width (and not just height).


With this in mind, we can deduce that B is closest to the light source, followed by C, and then A.


Therefore the answer is option (1).


As a matter of MCQ strategy, students could have immediately eliminated options (3) and (4) as the actors do not line up in the correct order (A, B and C from left to right).


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