The refractive indices of Kerosene, Turpentine and water are 1.44, 1.47 and 1.33 respectively. Light will have maximum speed in:

  1. Kerosene
  2. Turpentine
  3. Water
  4. Speed remains same for all

Answer (Detailed Solution Below)

Option 3 : Water
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RRB NTPC CBT-I Official Paper (Held On: 4 Jan 2021 Shift 1)
100 Qs. 100 Marks 90 Mins

Detailed Solution

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The correct answer is Water.

Key Points

  • Refractive Index is the ratio of the light's speed in a vacuum to its speed in a specified medium.
  • It is a dimensionless quantity.
  • Formulae are given for the refractive index
    • n = c/v
    • n = refractive index
    • c = velocity of light in a vacuum.
    • v = velocity of light in a specified medium.
  • From the given formulae we get, the Refractive index is the inverse relation to Light's speed.
  • The refractive index of the material is high, then the light's speed will be low and vice-versa.
  • In the given question, the refractive indices of Kerosene, Turpentine, and water are 1.44, 1.47 and 1.33, respectively.
  • So, the water has the lowest refractive index among all so, the speed of light will be maximum in water.
  • Turpentine has the highest refractive index, so the speed of light will be low in the Turpentine.

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