Practise Microscopy. 21 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Required practical:Microscopy (method, variables and exam tips)
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Microscopes are used to look at cells.
(a) Which equation is correct? Tick (✓) one box.[1]
magnification = size of image ÷ size of real object
magnification = size of real object ÷ size of image
magnification = size of image × size of real object
magnification = size of image − size of real object
(b) A light microscope has an eyepiece lens with a magnification of ×10 and an objective lens with a magnification of ×40. Calculate the total magnification.[1]
(c) The image of a cell is 20 mm wide. The magnification is ×400. Calculate the real width of the cell in mm.[2]
(d) Give the real width of the cell in micrometres (µm). 1 mm = 1000 µm[1]
Show the answer and mark scheme
(a)Answer: magnification = size of image ÷ size of real object
(b)Answer: ×400
(10 × 40 =) 400 (×)
(c)Answer: 0.05 mm
20 ÷ 400
0.05 (mm)
(d)Answer: 50 µm
50 (µm)
Question 2Medium8 marks
A student used a light microscope to observe onion epidermis cells.
(a) Describe how the student should prepare a slide of onion epidermis cells.[3]
(b) Give one reason why the student added a stain to the cells.[1]
(c) The student made a drawing of some of the cells. Give two rules the student should follow when making a scientific drawing.[2]
(d) The student also looked at human cheek cells. Give two structures the student would see in the onion cells that would not be seen in the cheek cells.[2]
Show the answer and mark scheme
(a)
peel off a thin layer of epidermis (using forceps)
place it flat on a (drop of water on a) microscope slide
add a drop of iodine solution / stain
lower a coverslip at an angle / carefully to avoid trapping air bubbles
(b)
to make the cells / nucleus easier to see / to increase contrast
(c)
use a sharp pencil
use clear, continuous lines (no sketching)
no shading / colouring
draw only what is seen / keep structures in proportion
draw label lines with a ruler / label lines should not cross
include a title / magnification / scale bar
(d)
cell wall
(permanent) vacuole
Question 3Hard8 marks
A student wanted to estimate the mean length of onion epidermis cells using a light microscope.
(a) Describe a method the student could use. You should include how the student would prepare the slide and how they would estimate the mean length of the cells.[6]
(b) At a magnification of ×100, the diameter of the field of view was 1.8 mm. The student counted 9 cells end to end across the diameter. Calculate the mean length of one cell in µm.[2]
Show the answer and mark scheme
(a)
peel a thin layer of epidermis with forceps and lay it flat on a microscope slide in a drop of water
add iodine solution to stain the cells and lower a coverslip at an angle to avoid air bubbles
focus on the lowest power objective with the coarse focus, then use the fine focus / move to a higher power
measure the diameter of the field of view by placing a clear ruler (with mm divisions) on the stage at the same magnification
count the number of cells that fit end to end across the diameter of the field of view
mean length of one cell = diameter of field of view ÷ number of cells
repeat in several different areas of the slide / with several slides and calculate a mean
convert the answer to µm (1 mm = 1000 µm)
Marked with levels of response: the full level descriptors are in the app.