Spectrum of electromagnetic radiation - class-XI

UV spectroscopy (400-700nm) is a type of absorption spectroscopy in which light of ultra-violet region is absorbed by the molecule resulting in the excitation of the electrons from the ground state to higher energy state. It obeys the Beer-Lambert law that states that when a beam of monochromatic light passes through a solution of an absorbing substance, the rate of decrease of intensity of radiation with the thickness of the absorbing solution is directly proportional to the incident radiation as well as the concentration of the solution.

In a spectrophotometer, the spectrometer produces the desired range of wavelength of light from a wide range of wavelengths. Transmittance (T) is the percentage of sample transmission and is defined as the fraction of light that passes through the sample. It is related to absorption by the expression 

Monochromator filters/allows only a single/particular wavelength of light to pass through the solution.

UV spectroscopy is a type of absorption spectroscopy in which light of ultra-violet region is absorbed by the molecule resulting in the excitation of the electrons from the ground state to higher energy state. A photometer is a part of a UV spectrophotometer and measures light intensity or the optical properties of solutions. Thus the correct answer is option A.

A photometer is an instrument that measures the strength of electromagnetic radiations in the ultraviolet, visible and the infrared spectrum. Most of the photometers convert light into electric current with the help of a photoresistor. photodiode or a photomultiplier. 

The reaction center of photosystem I (PSI) is referred to as $ P _{700}$ where "P" stands for "Pigment" and "700" stands for the wavelength of light that this particular chlorophyll molecule absorbs most strongly. The reaction center of photosystem II (PS II) is referred to as $ P _{680}$ for comparable reasons. 

Jan Ingen-Housz showed that sunlight is essential for photosynthesis. He concluded that green plants purify the air in presence of sunlight. Thus, option A is the correct answer.

The visible spectrum of electromagnetic radiation ranges from approximately 0.4 micrometers (violet) to 0.7 micrometers (red).

EMR is the standard abbreviation for Electromagnetic Radiations, which are waves of the electromagnetic field.

Solar radiation travels through the vacuum of space as electromagnetic waves, which do not require a medium to propagate.