Questions on Light
Q9. A pupil is observing the behaviour of a woodpecker. He uses a periscope to look over a wall at a tree, and waits for the bird to land on the trunk. The pupil can only watch one part of the tree trunk at a time.
![](Lightgraphic9ans.png)
(a) Which point on the tree trunk which he can see using the periscope in the position shown.
Point D ![](../../../graphics/symbols/nuclides/ticksmall.png)
1 mark
(b) Draw the path for a ray of light on the diagram to show how the pupil sees this point.
See diagram
Ray drawn as solid line with arrow on it. ![](../../../graphics/symbols/nuclides/ticksmall.png)
Angle of incidence roughly equal to angle of reflection at each mirror![](../../../graphics/symbols/nuclides/ticksmall.png)
Ray direction must go from the tree to the pupil's eye.![](../../../graphics/symbols/nuclides/ticksmall.png)
3 marks
(c) What should the pupil do to the periscope to watch point C?
To observe point C he should rotate the periscope so that it is almost vertical. ![](../../../graphics/symbols/nuclides/ticksmall.png)
1 mark
Maximum 5 marks