JEE Advanced 2016Paper 1
- Exam
- JEE Advanced
- Year
- 2016
- Paper
- Paper 1
- Subject
- Physics
- Chapter
- Thermal Properties of Matter
JEE Advanced 2016 · Paper 1 · Physics · Thermal Properties of Matter
An incandescent bulb has a thin filament of tungsten that is heated...
An incandescent bulb has a thin filament of tungsten that is heated to high temperature by passing an electric current. The hot filament emits black-body radiation. The filament is observed to break up at random locations after a sufficiently long time of operation due to non-uniform evaporation of tungsten from the filament. If the bulb is powered at constant voltage, which of the following statement(s) is(are) true?
Options
- AThe temperature distribution over the filament is uniform
- BThe resistance over small sections of the filament decreases with time
- CThe filament emits more light at higher band of frequencies before it breaks up
- DThe filament consumes less electrical power towards the end of the life of the bulb
Correct answer
C. The filament emits more light at higher band of frequencies before it breaks up
Step-by-step solution
Because of non-uniform evaporation at different section, area of cross-section would be different at different sections.
Region of highest evaporation rate would have rapidly reduced area and would become break up cross section.
Resistance of the wire as whole increases with time.
Overall resistance increases hence power decreases. At break up junction temperature would be highest, thus light of highest band frequency would be emitted at those cross-section.
Region of highest evaporation rate would have rapidly reduced area and would become break up cross section.
Resistance of the wire as whole increases with time.
Overall resistance increases hence power decreases. At break up junction temperature would be highest, thus light of highest band frequency would be emitted at those cross-section.