Question

The use of fluorescent light tubes for lighting homes, offices etc are very common. Also , in the advertisements displayed in front of offices , shops etc., you have quiet often seen use of colures light tubes.To reduce the consumption of electricity , use of CFLs (compact fluorescent lamps light bulbs ) is becoming very popular . To further cut consumption, now a days, we have LED (light emitting diodes) in the form of very efficient solid bulbs grouped in clusters .

Now, answer the following question:

(i) How do differ from fluorescent light tubes? What is the basic principles? What harm they do to the atmosphere after they are discarded?

(ii) How do LED bulbs differ from CFL bulbs?

(iii) A laymen asks you how different colors are obtained in the light tubes of advertisements? How would you explain this to him?

Answer 1

(i) Fluorescent light tubes are cathode ray tubes coated with a suitable material ( called phosphor) which produces visible light when hit by cathode rays. CFLs are simply miniature versions of full-sized fluorescent. They ** into standard lamp sockets and give light similar to the fluorescent light tubes. They are more efficient. They contain mercury vapuors. When, broken mercury vopours enter into atmosphere and cause health hazards.

(ii) LED bulbs do not contain mercury and hence are eco-friendly. They consume less electricity than CFLs. Moreover, they last longer than CFLs.

(iii) The light tubes emitting different colors are basically discharge tubes. The of the light emitted depends upon the gases taken inside the discharge tube and the of the glass. For example, neon in colorless tubes produces orange red light and deep red in light red tube. Similarly, a mixture of neon, argon and mercury vapor emit light blue, dark blue and light green light depending upon weather the tube colorless, purple or green.