What is the total magnification when using a 10x eyepiece and a 40x objective lens?
40x
100x
400x
4,000x
The Correct Answer is C
A. 40x: 40x represents only the magnification of the objective lens alone. Total magnification is calculated by multiplying the objective lens magnification by the eyepiece magnification, so 40x alone does not reflect the combined power.
B. 100x: 100x would result from a 10x eyepiece combined with a 10x objective lens, not a 40x objective. Using the wrong combination for calculation would underestimate the actual total magnification.
C. 400x: Total magnification is calculated by multiplying the eyepiece (10x) by the objective lens (40x): 10 × 40 = 400. This total magnification allows clear visualization of medium-sized bacterial cells under the light microscope.
D. 4,000x: 4,000x would be achieved with much higher objective lenses, such as an oil immersion 400x objective combined with a 10x eyepiece. Using 40x for the objective does not reach this level of magnification.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Alpha hemolysis is characterized by partial lysis of red blood cells on blood agar, leading to a greenish or brownish discoloration around bacterial colonies rather than a clear zone. This occurs because the bacteria produce hemolysins that oxidize hemoglobin to methemoglobin, causing the greenish hue, but do not completely lyse the red blood cells. In contrast, beta hemolysis results in complete destruction of red blood cells and a clear zone surrounding the colonies. Therefore, alpha hemolysis produces incomplete hemolysis with color change rather than full destruction and clearing of the agar.
Correct Answer is A
Explanation
A blood agar plate is a nutrient-rich culture medium that contains mammalian blood, usually 5% sheep blood, mixed with agar. It is commonly used in microbiology laboratories to grow and differentiate bacteria based on their ability to lyse red blood cells (hemolysis). The red color of the medium comes from the intact red blood cells, and bacterial colonies may produce clear zones (beta hemolysis), greenish zones (alpha hemolysis), or no change (gamma hemolysis) around them. This property helps in identifying clinically important bacteria such as Streptococcus species.
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