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Questions on Light

Q13. The diagram shows two rays of light coming from a point source, reflecting in a plane mirror, and entering a person's eye. The person sees an image of the light source at a point behind the mirror.

(a) On the diagram, draw construction lines to find the position where the image appears. Label the image I.

Either the dashed construction lines - - - -   tracing the rays back to a virtual image point or the dotted lines ....... must be drawn

1 mark

(b)

(i) The person moves further away from the mirror. How does this affect the position of the image relative to the mirror?

The image is in the same place relative to the mirror - the image is not an image of the person - the object that the image is formed from does not move - so the image won't either!

1 mark

(ii) The point source of light is moved closer to the mirror. How does this affect the position of the image?

It is closer to the mirror

Each point on an image is always as far behind the mirror as that point on the object is in front of it.

1 mark

The diagram below shows two rays of light coming from a small fish in some water. The rays enter a person's eye.

(c) The person sees an image of the fish under the water. On the diagram, draw construction lines to find the position of the image. Label the image I.

See diagram

The brain thinks that the rays travel in straight lines from a point - it therefore traces the path back to a point where they would emenate from. A virtual image of the fish is seen at that point - higher up in the water than it really is!

1 mark

(d) In some parts of the world, people catch fish using spears. When they see the image of a fish in the water, where should they aim?

Below the apparent position of the fish

1 mark

Maximum 5 marks