In ear, nose, and throat (ENT) examination, the head mirror worn by doctors is which type of mirror used to focus light?
-
AA concave mirror that converges light into a focused beam
-
BA plain plane mirror that only reflects light without focusing
-
CA convex mirror that spreads light over a wide area
-
DA plano convex lens used instead of a mirror
Answer
Correct Answer: A concave mirror that converges light into a focused beam
Explanation
Introduction / Context:ENT specialists often use a distinctive circular mirror worn on the head to examine the throat, nose, and ear of a patient. This classic device helps doctors direct a strong beam of light into body cavities. The question asks what type of mirror this head mirror actually is.
Given Data / Assumptions:
- The device is called a head mirror and is used in medical examination.
- It reflects light from an external source into the patient body region being examined.
- We must decide whether it is concave, convex, plane, or a lens.
- We assume standard optics: concave mirrors converge light, convex mirrors diverge light, and plane mirrors reflect without focusing.
Concept / Approach:For detailed examination of small cavities like the throat or ear, a doctor needs a bright, focused beam of light. Concave mirrors are known for converging parallel rays of light to a focal point. When the doctor adjusts the mirror so that the focus falls on the area of interest, the region becomes brightly illuminated. A convex mirror would scatter the light, and a plane mirror would not focus the beam. Therefore, the head mirror is a concave mirror with a hole in the center through which the doctor looks along the light beam.
Step-by-Step Solution:
Step 1: Recall the basic property of concave mirrors: they can form a focused beam by converging reflected light rays toward a focal point. Step 2: Remember that ENT doctors want to direct a concentrated beam of light into small spaces, so a focusing device is required to increase brightness in that region. Step 3: Recognize that a convex mirror would spread light out, reducing the intensity on a small target area, which is the opposite of what is needed for examination. Step 4: Understand that a plane mirror would simply reflect light without concentrating it, leading to lower intensity and less effective illumination. Step 5: The head mirror design uses a circular concave mirror with a central hole. Light from a lamp is reflected by this concave surface and concentrated onto the patient area while the doctor looks through the central opening. Step 6: Therefore, the correct description is that the head mirror is a concave mirror that converges light into a focused beam.Verification / Alternative check:Diagrams of classic ENT examination instruments show the head mirror with a concave reflecting surface. Explanations in physics and medical equipment textbooks mention that the concave mirror focuses light at a point, enhancing visibility in dark cavities. These descriptions match the converging property of concave mirrors and confirm that the head mirror is not plane or convex.
Why Other Options Are Wrong:
- The plain plane mirror option is wrong because it would not concentrate light and would give poor illumination.
- The convex mirror option is wrong because convex mirrors diverge reflected rays, making the light more spread out and less intense.
- The plano convex lens option is wrong because the device in question is a mirror, not a lens, and it works by reflection rather than refraction.
Common Pitfalls:Some learners think any small curved mirror used in instruments is convex, perhaps because convex mirrors are common in vehicles. Others assume a plane mirror because they focus only on reflection, not on concentration of light. To avoid confusion, remember the basic rule: when you need a bright focused spot of light, a concave mirror or a converging lens is used, not a convex mirror or a simple plane mirror.
Final Answer:A concave mirror that converges light into a focused beam