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How does the speed of light determine the optical density of a medium? - Physics

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प्रश्न

How does the speed of light determine the optical density of a medium?

थोडक्यात उत्तर
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उत्तर १

If the speed of light in a medium is less than the speed of light in air, means the MEDIUM is DENSER than air.
If the speed of light is more than the speed of light in AIR, means the MEDIUM is LESS DENSER than air.
Speed of light is 1/density of medium

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उत्तर २

  1. Definition of Optical Density: Optical density refers to how much a medium can slow down the speed of light compared to its speed in a vacuum.
  2. Speed of Light in Different Media: Light travels fastest in a vacuum (c = 3 × 108 m/s). When light enters a medium (like water, glass, or air), its speed decreases depending on the medium's optical density.
  3. Relation Between Speed and Optical Density: The greater the optical density, the slower the speed of light in the medium. For example, light travels more slowly in glass than in air because glass has a higher optical density.
  4. Refractive Index: The optical density is quantified using the refractive index (n), which is defined as: `n = c/v`
  5. Example:
    • In air: n ≈ 1, light speed is almost the same as in a vacuum.
    • In water: n ≈ 1.33, light slows down significantly.
    • In glass: n ≈ 1.5, light slows down even more.
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पाठ 5: Light Energy - Short/long Answer Question [पृष्ठ ९९]

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सेलिना Concise Physics [English] Class 8 ICSE
पाठ 5 Light Energy
Short/long Answer Question | Q 2 | पृष्ठ ९९

संबंधित प्रश्‍न

In the following diagram, the path of a ray of light passing through a glass prism is shown:

In this diagram the angle of incidence, the angle of emergence and the angle of deviation respectively are (select the correct option):

(A) X, R and T

(B) Y, Q and T

(C) X, Q and P

(D) Y, Q and P


Study the following ray diagram:

In this diagram, the angle of incidence, the angle of emergence and the angle of deviation respectively have been represented by

(A) y, p, z

(B) x, q, z

(C) p, y, z

(D) p, z, y


As light rays emerge from a glass prism into air, are they refracted towards or away from the normal?


A beam of white light is shone onto a glass prism. The light cannot be:
(a) deviated
(b) dispersed
(c) focused
(d) refracted


What do you understand by the term spectrum? Name the various colours present in the spectrum of sunlight.


Complete the ray diagram given below to show the nature of light produced on the screen.


Refer to fig

(i) Name the lens L.

(ii) What are the points O, O' called?

(iii) Complete the diagram to form the image of the object AB.

(iv) Write three characteristics of the image.


An object AB is placed in front of a convex lens as shown in fig. 4. Complete the ray diagram and obtain the image formed and state the nature of the image.


Suggest one way, in each case, by which we can detect the presence of Infrared radiations.


A ray of light is incident at 45° on an equilateral prism in the diagram below.

  1. Name the phenomenon exhibited by the ray of light when it enters and emerges out of the prism.
  2. State the cause of the above phenomenon mentioned by you.

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