Required Practical 1: microscopes

Question 1

what is found at the centre of the microscope?

Answer 1

the stage

Question 2

where are clips found and what is their purpose?

Answer 2

found on the stage to help keep the slide in place

Question 3

What is below the stage?

Answer 3

A lamp

Question 4

what is the purpose of the lamp?

Answer 4

passes light up through the microscope slide

Question 5

name the features of a microscope

Answer 5

stage
clips
lamp/mirror
lenses usually (4x)(10x)(40x)
coarse focussing dial
fine focussing dial

Question 6

some microscopes are different and don’t have a lamp, what might these microscopes use to see the image on the slide?
how does this work?

Answer 6

Mirror,

the mirror is used to reflect light up through the microscope slide

Question 7

where is the mirror located?

Answer 7

beneath the stage

Question 8

what is above the stage?

Answer 8

lenses

most microscopes have 3 lenses

Question 9

what magnification do most microscope lenses have?

Answer 9

4x 10x and 40x

Question 10

what is at the top of the microscope?

Answer 10

the eyepiece(where we look through)

Question 11

what does the eyepiece contain?

Answer 11

the eyepiece lens which usually has a magnification of 10x

Question 12

where is the coarse focussing dial and the fine focusing dial located?

Answer 12

on the sides of the microscope

Question 13

how do we view an optical microscope using a prepared slide?

Answer 13

1. first we place the slide onto the stage and use the clips to hold the slide in place
   2.then select the lowest power objective lens which is usually 4x
   3.We position the objective lens so it almost touches the microscope slide(to do this we slowly turn the coarse focussing dial)
   its very important that we look at the microscope from the side while we adjust the position of the objective lense.
   4.when the objective lens almost touches the slide, we stop turning the dial
   if we look through the eyepiece while positioning the objective lens, there is a risk that we damage the slide.
2. at this stage we look down through the eyepiece
3. now we need to slowly turn the coarse focussing dial. this increases the distance between the objective lense and the slide. we do this until the cells come into focus.
4. We now use the fine focussing dial to bring the cells into a clear focus

Question 14

what equation is used to calculate the total magnification?

Answer 14

magnification of eyepiece lens x magnification of objective lens
10x X 4X

Question 15

what is the magnification of the low-power objective lens?

Answer 15

4x

Question 16

calculate the total magnification when we use the low-power objective lens

Answer 16

40x
magnif of eyepiece X magnif of objective lens used= total magnification
10x X 4x = 40x

Question 17

calculate the total magnification when we use the higher power objective lens such as the 10x

Answer 17

100x
magnif of eyepiece X magnif of objective lens= total magnif
10x X 10x = 100x

Question 18

Label the animal cell structures seen in the microscope

Answer 18

this depends on what animal cell is shown on the slide but typically : cell membrane
nucleus
cytoplasm
tiny flecks may be mitochondria

with an optical microscope, only limited features are seen, whereas if we wanted to see other features such as the ribosomes, we would need an electron microscope

Question 19

under a light microscope what can you expect to see in a plant cell?

Answer 19

cytoplasm
nucleus
cell wall
depending on type of plant cell:
may see vacuole
may see chloroplasts

Question 20

how do you draw a magnification scale?

Answer 20

1. place a clear plastic ruler over the stage
2. measure diameter of the field of view in millimetres
3. show this on drawing using a scale bar
4. Rite the magnification too e.g. 100x