The number of following statement/s which is/are\(\text{\underline{ incorrect}}\) is______ (A) Line emission spectra are used to study the electronic structure (B) The emission spectra of atoms in the gas phase show a continuous spread of wavelength from red to violet (C) An absorption spectrum is like the photographic negative of an emission spectrum (D) The element helium was discovered in the sun by spectroscopic method.
The task is to identify the number of incorrect statements from the given options. Let's evaluate each one:
(A) Line emission spectra are used to study the electronic structure. Correct - Line emission spectra arise due to electronic transitions and help in understanding electronic structure.
(B) The emission spectra of atoms in the gas phase show a continuous spread of wavelength from red to violet. Incorrect - Emission spectra of atoms in the gas phase are characterized by discrete lines, not a continuous spectrum. Continuous spectra are typical of solids or dense gases.
(C) An absorption spectrum is like the photographic negative of an emission spectrum. Correct - This statement is true; an absorption spectrum features dark lines in place of the bright lines of an emission spectrum.
(D) The element helium was discovered in the sun by spectroscopic method. Correct - Helium was indeed discovered in the solar spectrum using spectroscopy.
In summary, only statement (B) is incorrect. Thus, the number of incorrect statements is 1, which falls within the expected range [1,1].
