Question

Which of the following instruments can be used to measure the illuminating power of two sources?
A. Lactometer
B. Manometer
C. Salinometer
D. Photometer

Answer 1

Hint:Photometry is the measurement of brightness, in the form of intensity, of light that our eyes can perceive. Photometer is an instrument used in photometry. We must be aware of all the terms mentioned in question to solve it.

Complete answer:
Photometer is the instrument that is used to measure the illuminating power of two sources.It is an instrument used in Photometry to measure the light. It measures the light intensity by converting light to electric current and then measuring current intensity. It also measures the different optical properties of solution by use of photodiodes, photomultiplier and photoresistors.

Other optical properties that can be measured by photometer are: Luminescence, Fluorescence, Reflection of light, Scattering of light, Illuminance, Phosphorescence, Absorption of light and Irradiance. Lactometer is an instrument used to measure the density of milk by its specific gravity. It can also be taken as a purity tester of milk.

Manometer is the device to measure pressure of any liquid or gas and is one of the most accurate devices to measure pressure.Salinometer measures the salinity of the solution. It only measures the amount of salt dissolved in solution and not the undissolved quantity.

Therefore, the correct answer is option B.

Note:Another method of working of a photometer is by measurement of strength of EM radiation that is present in UV to infrared range. It measures the light wavelength after filtering light by monochromator.