What is the actual width of a kidney if its shadow measures 9 cm with an OID of 18 cm at a 105-cm SID?

To determine the actual width of the kidney based on the shadow measurements, we can use the formula that relates the size of the object, the size of its shadow, the Object-to-Image Distance (OID), and the Source-to-Image Distance (SID):

[ \text{Actual Width} = \text{Shadow Width} \times \frac{\text{OID} + \text{SID}}{\text{OID}} ]

In this scenario:

• The shadow measures 9 cm.

• The OID is 18 cm.

• The SID is 105 cm.

Plugging the values into the formula gives:

[

\text{Actual Width} = 9 , \text{cm} \times \frac{18 , \text{cm} + 105 , \text{cm}}{18 , \text{cm}}

]

Calculating the numerator:

[

18 , \text{cm} + 105 , \text{cm} = 123 , \text{cm}

]

Now substituting back into the formula:

[

\text{Actual Width} = 9 , \text{cm} \times \frac{123 ,