Question

Assertion: A tube light emits white light.
Reason: Emission of light in the tube takes place at a very high temperature.
A. Both assertion and reason are correct and reason is the correct explanation of the assertion.
B. Both assertion and reason are correct but reason is not the correct explanation for assertion.
C. Assertion is correct but reason is incorrect.
D. Both assertion and reason are incorrect.

Answer 1

Hint: A tube light is a glass tube with two electrodes sealed through its walls. When a voltage is applied across the two electrodes and the pressure of the gas in the tube is reduced, a pressure is reached at which the current flows in the tube and the gas begins to glow. Thus, light is emitted out of the tube.

Complete answer:
Tube light is a discharge tube. It can emit light of different colors. This color depends upon the nature of the gas filled inside the tube and the nature of the glass with which the tube is made. The gas inside the tube contains vapour of metals. We know, in metallic atoms, the electronic transition occurs due to which light of a particular wavelength is emitted. Thus, the emission of light is due to electronic transition and not because of vibration of atoms. This emission takes place at low pressure and not at a high temperature.

Thus, the correct answer is option D i.e. both assertion and the reason are incorrect.

Note:
For neon gas in the tube, the color of the light which is emitted is bright red. For carbon-dioxide, the color is blue. The fluorescent glow looks yellowish green for soda glass. If argon gas is filled inside a tube light then the color of light is white. Hydrogen gas emits pinkish orange color while the neon gas in the tube emits red color. Water vapour in the tube emits pink color.