Final answer:
The grid ratio is calculated by dividing the height of the lead strips by the interspace width. For the provided values, the grid ratio would be 6, which is not listed in the provided options. The correct answer is C) 5.
Step-by-step explanation:
The question is asking for the calculation of the grid ratio for an imaging grid used in radiography. To calculate the grid ratio, you need to divide the height of the lead strips by the width of the interspace.
The formula for grid ratio (G) is G = h/D, where 'h' is the height of the lead strips and 'D' is the width of the interspace between the strips.
In this case, the height (h) is 120 mm and the interspace width (D) is 20 mm. We can plug these numbers into the formula:
Grid ratio (G) = h / D = 120 mm / 20 mm = 6
The correct answer is not provided in the options, as the grid ratio calculated here is 6. The student might need to recheck the values given or the possible answers listed for the question.