Physics Class 10 Practical 23 Important Viva Questions with Answers (refractive index of water by using concave mirror )

 

1. What is the refractive index?

   • The refractive index is a measure of how much light bends when it passes from one medium into another. It is the ratio of the speed of light in a vacuum to the speed of light in the medium.

2. What is the principle behind using a concave mirror to measure the refractive index of water?

   • The principle involves measuring the real and apparent depth of an object submerged in water. The refractive index can be calculated using the formula $n = \frac{\text{Real depth}}{\text{Apparent depth}}$.

3. What apparatus and materials are required for this experiment?

   • The experiment requires a concave mirror, a beaker of water, a needle or pin, a ruler, and a stand to hold the needle or pin.

4. How do you set up the experiment?

   • Place the concave mirror at the bottom of the beaker filled with water. Suspend a needle or pin vertically above the mirror, and adjust its position until its image is clearly visible in the mirror. Measure the real and apparent depths.

5. What is real depth?

   • Real depth is the actual depth of the object (needle or pin) below the surface of the water.

6. What is apparent depth?

   • Apparent depth is the depth at which the object appears to be when viewed from above the surface of the water due to refraction.

7. How do you measure the real and apparent depths?

   • Real depth is measured from the surface of the water to the mirror. Apparent depth is measured from the surface of the water to the point where the image of the needle or pin appears to be in the water.

8. What formula is used to calculate the refractive index of water in this experiment?

   • The refractive index $n$ is calculated using the formula $n = \frac{\text{Real depth}}{\text{Apparent depth}}$.

9. Why does the apparent depth differ from the real depth?

   • The apparent depth differs from the real depth due to the bending of light rays when they pass from water (a denser medium) to air (a less dense medium), making the object appear closer to the surface than it actually is.

10. What is the typical value of the refractive index of water?

    • The typical value of the refractive index of water is approximately 1.33.

11. Why is a concave mirror used in this experiment?

    • A concave mirror is used because it helps form a clear, focused image of the needle or pin, making it easier to measure the apparent depth accurately.

12. How does the curvature of the concave mirror affect the experiment?

    • The curvature of the concave mirror helps to magnify the image of the needle or pin, making it easier to locate and measure the apparent depth.

13. What precautions should be taken during the experiment?

    • Ensure the needle or pin is aligned vertically, measure depths accurately, avoid parallax error while reading measurements, and ensure the water surface is undisturbed.

14. What could be potential sources of error in this experiment?

    • Potential sources of error include incorrect alignment of the needle or pin, parallax error in reading measurements, and disturbances on the water surface affecting the image clarity.

15. How can you minimize errors in this experiment?

    • To minimize errors, carefully align the needle or pin, take multiple readings to average out errors, and ensure the water surface is calm and undisturbed during measurements.

16. What is parallax error, and how can it be avoided?

    • Parallax error occurs when the position of the observer’s eye affects the measurement. It can be avoided by ensuring that the eye is directly above the measurement scale and the object being measured.

17. How does temperature affect the refractive index of water?

    • The refractive index of water can vary slightly with temperature, as changes in temperature affect the density and optical properties of water.

18. Can this method be used to measure the refractive index of other liquids?

    • Yes, the same method can be used to measure the refractive index of other transparent liquids by replacing water with the liquid in question.

19. Why is it important to ensure that the needle or pin is vertical?

    • Ensuring the needle or pin is vertical is crucial for accurate measurement of the apparent depth and to avoid skewed readings.

20. How does the refractive index of water compare to that of other common substances?

    • The refractive index of water (approximately 1.33) is lower than that of glass (around 1.5) and higher than that of air (approximately 1.0).