The movement of tennis balls can be tracked using a set of linked high-speed fixed-focus cameras placed around the court. The balls position is measured and its trajectory reconstructed. A tennis ball has a diamer of 67mm. When the ball is 10 metres from the camera, a sharp image of it is formed on a CCD 55mm behind the lens .

a)

i) Calculate the magnification of this image [1]

ii) Show that the power of the lens in the fixed focus camera is about 18D. [2]

iii) Show that the diameter of the image of the ball on the CCD is about 0.4mm. Make your method clear [2]

b) There are 70 pixels per mm on the CCD

i) Calculate the number of ipixels across the image of the 67mm diameter ball. [1]

ii) As the ball moves, its image moves across the CCD

Calculate the least distance the ball must move sideways for its image to move 1 pixel. [1]

c) The position of hte ball on 2 consecuative images can be used to determine the distance it has moved between images. Two such images give a value for the distance moved of 0.080m

State and explain the maximum possible value for this measurement based on your naswer to bii

Maximum Possible Value:

Explanation:

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