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Atoms — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsAtoms1 Mark
MCQ
For question two statements are given$-$one labelled Assertion $(A)$ and the other labelled Reason $(R).$ Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion $(A):$ A tube light emits white light
Reason $(R):$ Emission of light in a tube takes place at a very high temperature.
  • 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.
  • ✓
    $A$ is false and $R$ is also false.
✓

Answer

Correct option: D.
$A$ is false and $R$ is also false.
The tube light is nothing but a gas discharge tube, which can emit light of different colours.
This colour depends mainly upon the nature of the gas inside the tube and the nature of the glass.
For neon gas the colour is bright red and for $CO_2$ it is bluish.
Again, the fluorescent glow looks yellowish green for soda glass.
So it is the nature of the glass and the gas inside the tube which determines the colour of the fluorescent glow.
As argon is filled inside a tube tight, the colour of the light is white.

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