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M.C.Q-[Phy-1M]

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MCQ 11 Mark
In the following diagram showing dispersion of white light by a glass prism, the colours $\mathbf{P}$ and $\mathbf{Q}$ respectively are-
Image
  • Violet and Red
  • B
    Orange and Green
  • C
    Red and Blue
  • D
    Red and Violet
Answer
Correct option: A.
Violet and Red
(A) Violet and Red
Explanation:
The splitting of white light into its constituent colours is known as light dispersion. The spectrum is the band of seven colours produced by splitting white light. All of the constituent colours of white light have the same velocity in vacuum, but their velocity changes when they pass through a transparent 'medium' like a glass prism. Different colours are diverted by different angles on the prism's initial face. Violet's minimum speed is deviated by the maximum angle, whereas red's maximum speed is distorted by the minimum angle. As a result, the letters ' P ' and ' Q ' are violet and crimson, respectively.
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MCQ 21 Mark
Which of the following statement is/are true?
A. The speed of all colours is the same in air or vacuum.
B. The speed of all colours is different in denser media.
C. Speed of light in air is $3 \times 10^{8} \mathrm{~ms}^{-1}$.
D. Refractive index has no unit.
  • A
    A and B
  • B
    B and D
  • All of these
  • D
    A, B and C
Answer
Correct option: C.
All of these
(C) All of these
Explanation:
All the given statements are correct.
- The speed of all colours is the same in air or vacuum i.e. $3 \times 10^{8} \mathrm{~ms}^{-1}$. But the speed of all colours is different in a denser medium.
- The refractive index has no unit since it is a ratio. The absolute refractive index of a medium ( $\mathrm{n}_{\mathrm{m}}$ ) is given by $n_{m}=\frac{c}{v}$ where c is the speed of light in air, and v is the speed of light in the medium.
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M.C.Q-[Phy-1M] - Science STD 10 Questions - Vidyadip