For acquainting the students of applied physics and students of teaching physics with the concept of energy efficiency, electrical and spectral characteristics of two widely used lamps--integrated fluorescence lamp and common light bulb have been investigated. Characterization of the lamps has been done by measuring the spectral irradiance and constructing the voltage-current characteristics. Breaking voltage, electric resistance, energy efficiency, energy consumption and intensity spectral distribution, were determined. Also, the quantity of mercury present in the fluorescence lamp was determined by analysis of the spectral characteristics. The energy efficiency advantage of the fluorescence lamp over the common light bulb was shown through comparison of the examined parameters of the two lamps.