A student has to observe a permanent slide of binary fission in amoeba. Find the correct sequence of steps given below for focussing the object under a microscope. (a) Place the slide on the stage, look through the eye-piece and adjust the mirror to get proper illumination. (b) Focus the slide sharp using fine adjustment screw. (c) Look through the eye-piece and raise the objective lens using coarse adjustment screw till the object is focussed. (d) Look through the eye-piece and move the slide till the object is visible.

To observe a slide under a compound microscope, a systematic procedure must be followed:

1. Step (a): First, place the slide on the stage, look through the eye-piece, and adjust the mirror to get proper illumination. Without light, nothing will be visible.
2. Step (d): Look through the eye-piece and move the slide until the specimen (object) is aligned directly under the objective lens and becomes visible.
3. Step (c): Use the coarse adjustment screw to raise or lower the objective lens (while looking through the eye-piece) until the object comes into rough focus.
4. Step (b): Finally, use the fine adjustment screw to sharpen the focus and get a clear, detailed view of the binary fission stages.

Why other options are incorrect:

• Option A (d, c, b, a): Suggests moving the slide and focusing before adjusting the illumination, which is incorrect because the field of view would be completely dark.
• Option B (a, b, d, c): Suggests using the fine adjustment screw (b) before locating the object (d) and using the coarse adjustment screw (c), which is practically impossible.
• Option D (a, c, d, b): Suggests using the coarse adjustment screw (c) before aligning the slide (d), which might result in focusing on an empty area of the slide.