Q. Flash light equipped with a new set of batteries, produces bright white light. As the batteries were out
A) The light intensity gets reduced with no change in its colour
B) Light colour changes first to yellow and then red with no change in intensity
C) It stops working suddenly while giving white light
D) Colour changes to red and also intensity gets reduced
Explanation
(d) As batteries wear out, temperature of filament of flash light attains a lesser value, therefore intensity of radiation reduces. Also dominating wavelength $(\lambda_{m})$ in spectrum, which is the red colour, increases.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.