Case Study:

During an eye examination, an ophthalmologist uses a small handheld instrument called an ophthalmoscope to observe the retina and other internal parts of the eye. The device contains a tiny mirror with a small hole at its center. When light from a bulb strikes the mirror, it gets reflected into the patient’s eye. The reflected light from the retina travels back through the hole, allowing the doctor to clearly observe the inner structures of the eye.

If you're curious about the physics behind this, you can dive deeper into how mirrors and lenses work to understand reflection and refraction in our detailed guide.

In one examination, the doctor noticed that when the mirror was slightly tilted, the reflected light no longer entered the patient’s eye properly, making the retina difficult to observe. The doctor adjusted the angle of the mirror so that the reflected ray entered the pupil directly. The instrument also uses a concave mirror to focus light into the eye, producing a brighter image of the retina.

While the doctor sees a clear image here, the type of image matters for diagnosis; learn the vital differences in real vs. virtual images and how lenses affect our vision.

The process works on the basis of the Laws of Reflection of Light and image formation by mirrors. Proper alignment of the mirror ensures maximum reflection and better visibility of internal eye structures. This simple use of reflection helps doctors detect eye diseases at an early stage.

The ophthalmoscope is just one example of medical technology. You might also want to explore how other optical instruments like microscopes and telescopes work to manipulate light. And for a fun side-trip into optics, find out why objects appear bent in water through the lens of refraction.

CASE-BASED QUESTIONS

 MCQ 

Q1. Which property of light allows the doctor to see the inside of the eye using the mirror device?

A. Refraction
B. Reflection
C. Dispersion
D. Diffraction

Q2. Why is a concave mirror used in the ophthalmoscope?

A. To spread light in all directions
B. To absorb light
C. To focus light into the eye
D. To produce rainbow colours

 Assertion-Reason 

Q3. Assertion (A): The doctor adjusts the angle of the mirror carefully during eye examination.
Reason (R): According to the Laws of Reflection of Light, the angle of incidence is equal to the angle of reflection.

A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true, but R is false.
D. A is false, but R is true.

 Application-Based 

Q4. When the mirror inside the ophthalmoscope was tilted incorrectly, the doctor could not clearly observe the retina. Explain why this happened.

Q5. How does the use of a concave mirror improve visibility inside the patient’s eye during examination?

 Data/Logic-Based 

Q6. During an eye check-up, the angle between the incident ray and the mirror surface was measured as 40°. Calculate the angle of reflection.

ANSWER KEY WITH EXPLANATION

A1: B. Reflection
 Explanation:  The ophthalmoscope works using reflection of light. Light reflected from the mirror enters the eye and helps the doctor observe internal structures.

A2: C. To focus light into the eye
 Explanation:   A concave mirror converges light rays and produces a bright focused beam, making the retina easier to observe.

A3: A. Both A and R are true, and R is the correct explanation of A.
 Explanation: The mirror must be adjusted properly because reflected light follows the Laws of Reflection of Light, where the angle of incidence equals the angle of reflection.

A4: When the mirror was tilted incorrectly, the reflected rays did not enter the pupil properly. As a result, sufficient light did not reach the retina, reducing visibility.

A5: A concave mirror focuses light into a narrow beam. This increases brightness inside the eye and helps the doctor see detailed internal structures clearly.

A6: 50°
 Explanation: The angle between the incident ray and mirror surface is 40°.
Therefore, angle of incidence = 90° − 40° = 50°.
According to the Laws of Reflection of Light:

  ∠i=∠r  

Hence, angle of reflection = 50°.

 Mastered this case study?  Put your skills to the test with our Physics Class 10 worksheets. For full exam prep, grab our solved practice papers to see model answers, or challenge yourself with our unsolved practice papers to simulate a real test environment.

HOTS EXTENSION QUESTIONS

Q1. If a plane mirror were used instead of a concave mirror in the ophthalmoscope, how would the brightness of the reflected light change? Explain your reasoning.

Q2. Suppose the mirror surface inside the device becomes rough due to scratches. Predict how this would affect the doctor’s ability to observe the retina clearly.

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