Question

Two laboratory thermometers are marked as 'A' and 'B'. The bulb of thermometer 'A' is wrapped in a white cloth and that of thermometer 'B' in black cloth. Both the thermometers are placed in sunlight for an hour. After one hour:

• A. both the thermometers will read the same temperature
• B. thermometer 'A' will show higher temperature than 'B'
• C. thermometer 'B' will show higher temperature than 'A'
  
• D. either of the thermometers can show higher temperature, depending upon their initial readings

Answer 1

The correct option is C thermometer 'B' will show higher temperature than 'A'


Thermometer 'B' will show higher temperature than 'A'.
This is because thermometer 'B' is wrapped by a black cloth. Black cloth absorbs the heat radiation from the sun and becomes hotter.
White cloth reflects the heat radiation from the sun and hence it stays colder than the black cloth.
The final thermometer reading does not depend on initial reading. This is because thermometers read the instantaneous temperature of the body in contact.