1. 1
   A student draws an image of a plant cell that is 45 mm long. She measures the actual length of the cell using a microscope as 0.09 mm.

   (a)

   Using the formula magnification = image size / actual size, what is the magnification of her drawing?

   [1 mark]

   • A×5
   • B×50
   • C×500
   • D×5000

   (b)

   The student wants to record the actual length of the cell in micrometres (µm) instead of millimetres. What is 0.09 mm converted to micrometres?

   [1 mark]

   • A0.9 µm
   • B9 µm
   • C90 µm
   • D900 µm

   (c)

   The student then draws a second cell at the same magnification (×500) and finds its image length is 60 mm. Calculate the actual length of this second cell in mm, showing your working.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A technician views a bacterial cell under a light microscope and states that its actual diameter is about 2 µm. If she draws the cell as an image 8 mm wide, what magnification has she used?

   (a)

   (Note: 1 mm = 1000 µm, so 2 µm = 0.002 mm)

   [1 mark]

   • A×4000
   • B×400
   • C×40
   • D×40000

   (b)

   The technician then compares the bacterial cell to a human cheek cell with an actual diameter of about 60 µm. Approximately how many times larger is the diameter of the cheek cell compared with the bacterial cell (2 µm)?

   [1 mark]

   • A3 times larger
   • B30 times larger
   • C300 times larger
   • D0.3 times larger

   (c)

   Explain why the technician needed to use a light microscope, rather than the unaided eye, to observe and measure the bacterial cell.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student produces a scale drawing of a plant cell that is 36 mm long in the image, at a magnification of ×300.

   (a)

   Calculate the actual length of the cell, giving your answer first in mm and then converted to µm, showing your working.

   [3 marks]

   (b)

   The student's teacher tells her that most plant cells are between 10 µm and 100 µm in actual length, but the calculated actual length of her drawn cell is 120 µm. Explain two possible reasons for this discrepancy and suggest how the student could check her result.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A laboratory technician is asked to compare the sizes of four specimens: a virus (about 0.1 µm), a bacterium (about 2 µm), an animal cell (about 20 µm) and a frog egg (about 3 mm).

   (a)

   Explain how the technician would calculate the magnification needed to produce a clear image of the bacterium at 8 mm wide, and explain the relationship between actual size and the equipment needed to view each specimen.

   [6 marks]

   (b)

   The technician wants to produce an image of the animal cell (actual size 20 µm) and the frog egg (actual size 3 mm) both drawn at the same final image width of 60 mm. Explain how she would calculate the magnification required for each specimen, and explain why the two magnifications would be so different despite the images being the same final size.

   [6 marks]

   Total for question 4: 12 marks

End of questions