Step 1: Understanding the Concept:
An endoscope is a medical instrument used for non-invasive viewing of internal organs. It consists of a bundle of optical fibers that transmit light into the body and carry the image back to the physician. The technology behind optical fibers is the principle that this question is asking about.
Step 2: Detailed Explanation:
1. An endoscope uses optical fibers to guide light over long, flexible paths.
2. An optical fiber is a very thin strand of glass or plastic that acts as a waveguide for light.
3. Light is sent down the fiber and is contained within it by a phenomenon called Total Internal Reflection (TIR).
4. Total Internal Reflection occurs when light travels from a denser medium to a rarer medium at an angle of incidence greater than the critical angle. In an optical fiber, the central core is denser than the outer cladding. Light rays entering the core strike the core-cladding boundary at a large angle and are repeatedly reflected back into the core, allowing them to travel along the fiber with very little loss of intensity.
5. This principle allows the image of the internal organ to be transmitted clearly through the flexible tube of the endoscope to the eyepiece or camera.
Step 3: Analyzing the Options:
- (A) Refraction is the bending of light as it passes from one medium to another, but it doesn't explain how light is guided along a curved fiber.
- (B) Simple reflection occurs from a surface like a mirror. While TIR is a type of reflection, "Total Internal Reflection" is the specific and correct principle for optical fibers.
- (C) Dispersion is the splitting of white light into its constituent colors, which is not the primary principle of an endoscope.
Step 4: Final Answer:
The working of an endoscope is based on the principle of total internal reflection. Therefore, option (D) is correct.