BIO 171 - Exam 3

A nanometer is defined as: A. 10-3 B. 10-6 C.10-9 D. 10-12 C. A nanometer is defined as one-billionth of a meter. 2. True or False: A nanometeris longer than a micrometer. False. A nanometer is 1,000 times smaller than a micrometer. 1. Resolution and contrast are two critical factors that influence your ability to see an object. Explain each. Resolution refers to the distance between two objects at which the objects still can be seen as separate. Poor or low resolution means two (or more) objects may appear as one. *Contrast is the difference in light absorbance between two objects. Poor contrast gives a high background and makes the visualization of multiple objects difficult. For instance, trying to identify 2 dark colored objects at night (low light = low contrast) versus the same 2 objects in the middle of a sunny afternoon (bright light against 2 dark objects = high contrast). 1. Assuming a constant (non-adjustable) light source power, identify the part of the microscope you would adjust to limit the amount of light entering the microscope. Select all that apply. A. Objective B. Condenser C. Iris diaphragm D. Eye piece C. The iris controls the amount of light that passes through the sample and into the objective lens. Thus, it can be adjusted (opened or closed) to alter the amount of light.