In a standard compound microscope, considering only the main optical components and ignoring the mirror and the observer's eye, which one of the following gives the correct sequence in which light passes through the instrument from the specimen towards the observer?

Introduction / Context:

A compound microscope uses several optical components to magnify a small specimen. Understanding the order in which light passes through these components is important for both basic physics and practical laboratory use. This question asks you to identify the correct sequence of main optical elements (excluding the mirror and the observer's eye) through which light travels from the specimen towards the observer.

Given Data / Assumptions:

• We consider a typical compound microscope setup.
• Light from a source is reflected by a mirror, passes through the condenser and specimen, then through the objective lens and eyepiece.
• The body tube simply holds the optical alignment between objective and eyepiece.
• The options list the order of components after the condenser.

Concept / Approach:

In a compound microscope, the condenser collects and focuses light onto the specimen placed on the stage. The objective lens, located just above the specimen, forms a real, inverted and magnified image of the specimen inside the body tube. This intermediate image lies near the focal plane of the eyepiece. The eyepiece (eye lens) then acts as a magnifier, producing a further magnified virtual image that the observer sees. Thus, after the condenser, light must pass first through the objective lens, then travel through the body tube where the intermediate image is formed, and finally through the eyepiece.

Step-by-Step Solution:

Verification / Alternative check:

Textbook diagrams of the compound microscope clearly show the order: mirror (or light source), condenser, specimen, objective lens, body tube and eyepiece. The options that place the condenser first, followed by the objective and then body tube and eyepiece, align with this standard layout. Including the eyepiece before the body tube or placing the condenser after the objective would contradict the usual design and ray diagrams.

Why Other Options Are Wrong:

Option A: Condenser → Objective lens → Eye piece → Body tube incorrectly places the eyepiece before the body tube, reversing the natural order of internal components.

Option B: Objective lens → Condenser → Body tube → Eye piece reverses the positions of objective and condenser, which is not how light is focused onto the specimen.

Option D: Eye piece → Objective lens → Body tube → Mirror reverses the entire logical order and even introduces the mirror after the eyepiece, which is physically impossible.

Common Pitfalls:

Students sometimes confuse the roles of objective lens and condenser. The condenser is always nearer to the light source and the specimen, focusing illumination, while the objective is the primary image forming lens closest to the specimen. Remembering this distinction helps in correctly ordering the components in any microscope question.

Final Answer:

The correct sequence is Condenser → Objective lens → Body tube → Eye piece.