Question

A technician places 50 ml of a 10^-1 dilution of raw milk onto a 2 cm x 2 cm section on a microscope slide. Observation of the stain shows an average of 25 cells per field of vision. The technician then determines the diameter of the field of vision to be 0.22 mm. How many cells in one mL of the original milk sample?

Answer 1

Size of section of microscopic slide is,

= 2 cm x 2 cm

= 20 mm x 20 mm

So, the area is 400 square mm

Size of one field of vision is 0.22 mm

So, the number of fields of vision in 400 sq.mm is,

= 400/0.22

= 1818.18

There are 25 cells per field of vision.

So, the number of cells in 400 sq.mm is,

= 25 x 1818.18

= 45454

The sample is diluted 10^-1 times.

So, the total number of cells in the original and diluted sample (50 ml) is,

= 45454 x 10

= 454540

Number of cells in 1 ml is,

= 454540/50

= 9090