Lens and Image

Topics: Lens, Eyepiece, Optics Pages: 6 (1855 words) Published: June 15, 2013
Practical 1: Microscopy
1. What happened to the stage when you turned the knob anti-clockwise (away from you)? The stage will move up when turned the coarse adjustment knob (large knob) anti- clockwise.

2. What happened to the stage when you turned the knob clockwise (toward you)? The stage will move down when turned the coarse adjustment knob (large knob) clockwise.

3. Observe the letter ‘I’ under low (i.e. objective X4 ) magnification. What do you notice about the image? The image of letter ‘I’ under low magnification is inverted/upside down.

4. Move the slide slowly to the left. What happens to the image? The image will move to the right when the slide move slowly to the left.

5. Centre a letter. Now move the slide slowly away from you. What happens to the image? The image appears nearer (towards us) when the slide move slowly away from us.

6. How far does the stage move from one complete turn of the fine adjustment knob? – estimate; view from side. The stage move up with such a small distances that is hard to be noticed after one complete turn of the fine adjustment knob.

7. Completely close the iris diaphragm. What effect has this had on your ability to see? Completely close the iris diaphragm affect the ability to see by decreasing the brightness and increasing the contrast. The image produced is dim and not clear at all.

8. Now gradually open the diaphragm record the effect on:
Intensity of light; The intensity of light increase
Your ability to see; The image become bright and clearer

9. Focus on the image, set the diaphragm so illumination is minimal. Move the condenser gradually so that it is as close to the slide as it can go. Move the condenser as far away from the slide as you can. What happens? The light intensity will decrease.

10. Now carefully rotate x10 objective into the light path. If necessary, bring image into focus by turning the fine focus knob only. What has happened to the degree of details you can see in the letter ‘I’ and surrounding paper? The letter ‘I’ can only be seen for a small portion under the x10 objective lens.

11. Open the diaphragm; can you still see the actual strands within the paper? Yes, the actual strands are within the paper when open the diaphragm.

12. Move the slide slowly to the right. What happens to the image? The image move to the left when the slide move to the right.

13. Did you notice any difference from the same procedure using the 4x objective? Try your hand again with the 4x objective. Yes, the 4x objective lens provide clearer and overall image.

14. Carefully and slowly rotate 40x objectives into place. Ensure the objective doesn’t CRASH into slide. If you encounter any resistance, STOP! Is the image in focus?
No, the image is not in focus.

15. If not, use the FINE adjustment only. Note the close proximity of the 40x objective and the slide. Any large movements produced by the coarse adjustment will cause the objective to crash through the slide. Is your illumination adequate?

The illumination is not adequate.

16. Open the diaphragm and record the changes.
The image is clearer and brighter.

17. Move the condenser up and down. Does your eye detect any changes produced by movement of the condenser? Yes, the condenser moving upwards will provide a clearer and bright image while the condenser moving downwards providing a dim image.

Ocular Objective Total magnification| 10x 4x 40x10x 10x 100x10x 40x 400x10x 100x 1000x|

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