STUDENT ID – 03185525
COURSE – BIOLOGY 101 A
SUBMITTED TO – SAMITA CHOWDHARY
BIOLOGY LAB REPORT
MICROSCOPES AND CELLS
Aim: To describe and identify the features of different models of compound microscopes. Also, to learn the use of a microscope to examine a slide of the letter e and a slide of threads.
Introduction: The microscope is designed to make objects visible that are too difficult to see with naked eyes. The most common kinds of microscopes used in biology lab are binocular or monocular light microscopes. Compound means that the scopes have a minimum of two magnifying lenses. Binocular microscopes have two eyepieces and monocular have only one eyepiece.
Materials required: Compound microscope, clear ruler, coverslips, lens paper, blank slides, prepared slides: letter e and crossed thread and dropper bottle with distilled water.
1. What are the different parts of the microscope?
2. What are the common variations between different models of a compound microscope?
3. What is the shape of the letter e under an ocular and binocular microscope?
4. What are the colors of thread seen under these two microscopes?
Hypothesis: There will be a difference of shapes of slides e and thread when viewed with different microscopes (ocular and binocular).
1. Obtain a compound light microscope and follow the directions given by the instructor. Carry the microscope in a correct manner, hold the arm in one hand and support the base in another hand.
2. Locate the parts of the microscope:
– Head: It supports the two sets of lenses. The ocular is the lens in the eyepiece, which has a magnification of 10x.
– Objectives: These are the three lenses on the revolving nosepiece. The shortest lens is typically 4x and is called the scanning lens. The intermediate lens is 10x and the longest is 40x.
– Arm: It supports the stage and condenser lens. The condenser lens is used to focus the light from the lamp through the specimen to be viewed. The height of the condenser can be adjusted by an adjustment knob. The iris diaphragm controls the amount of light passing through the specimen.
– Stage: It supports the specimen to be viewed.
– Base: It acts as a stand for the microscope and houses the lamp.
3. Clean the microscope lens. Adjust the focus on your microscope.
4. Plug in your microscope and turn on the light. Rotate the 4x objective into position using revolving nosepiece ring.
5. Place the letter slide on the stage and look through the ocular and bring the letter into the right focus. Observe the slide from different lenses and draw the shapes of the letter seen in the microscope.
6. Now, observe the same things for the slide in the binocular microscope.
7. Do same steps for the crossed threads slide as well with both ocular and binocular microscopes.
Observations: SLIDE e
1. Under the ocular microscope, if the slide is slowly moved to the right, the letter e moves to the left side. The image of the letter is e is inverted.
2. When the slide is observed under the 40x objective, one can see only half of the slide.
3. The working distance is greater in 10x objective than 40x.
4. The total magnification of the letter when the microscope is set is 40.
5. The diameters of the field of view for 4x, 10x and 40x objectives are 4mm, 2mm, and 1mm respectively.
6. The shape and size of e under a binocular microscope remains the same.
CROSSED THREADS SLIDE:
1. The slide of the thread looks exactly the same in the binocular microscope.
2. One can see only two colors at a time when the slide is observed under 10x objective.
3. The 4x objective has a shorter depth of field as compared to the 10x objective.
4. When the stage is moved upwards with the coarse adjustment until both threads are just on focus, the blue thread comes over the red one.
5. The 10x objective has a shorter depth of field than 40x.
Result: There is a change in the size and shapes of both the slides under an ocular microscope. There is no such change in the binocular microscope.