The number of following statement /s which is/are 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 wavelenght from red to violet
(C) An absorption spectrum is like the photographic negative of an emission spectrum
(D) The element helium was discoverd in the sun by spectroscopic method

STATEMENT-1: Line emission spectra useful in the study of atomic. Structure. STATEMENT-2: Each element has a unique line emission spectrum.

Figure shows the enegry levels P, Q, R, S and G of an atom where G is the ground state. A red line in the emission spectrum of the atom can be obtaned by an energy level change from Q so S . A blue line can be obtained by following energy level change

Read the following text and answer the following questions on the basis of the same: Spectrum Analysis and Astronomy Each element in the periodic table can appear in gaseous form and produce its own spectrum unique to that element. Hydrogen will not look like Helium, which wil not look like carbon which will not look like iron....and soon. Astrophysists can identify what kinds of materials are present in stars from the analysis of star's spectra. This type of study is called astronomical spectroscopy. The science of spectroscopy is quite sophisticated. From spectrum lines analysis astrophysists can determine not only the element, but the temperature and density of that element in the star. The spectral line also can tell us about any magnetic field of the star. The width of the line can tell us how fast the material is moving. We can learn about winds in stars from this. The shifting of spectral liens shift back and forth indicates that the star may be orbiting another star. The following table shows a rough guide for the relationship between the temperature of a star and the electromagnetic spectrum. If the spectrum of a star is red or blue shifted, then it can be used to infer its velocity along the line of sight. Edwin Hubble observed that more distant galaxies tended to have more red shifted spectra. This establishes the theory of expansion of the universe. Which nature of spectrum establishes the theory of the expanding universe?

Read the following text and answer the following questions on the basis of the same: Spectrum Analysis and Astronomy Each element in the periodic table can appear in gaseous form and produce its own spectrum unique to that element. Hydrogen will not look like Helium, which wil not look like carbon which will not look like iron....and soon. Astrophysists can identify what kinds of materials are present in stars from the analysis of star's spectra. This type of study is called astronomical spectroscopy. The science of spectroscopy is quite sophisticated. From spectrum lines analysis astrophysists can determine not only the element, but the temperature and density of that element in the star. The spectral line also can tell us about any magnetic field of the star. The width of the line can tell us how fast the material is moving. We can learn about winds in stars from this. The shifting of spectral liens shift back and forth indicates that the star may be orbiting another star. The following table shows a rough guide for the relationship between the temperature of a star and the electromagnetic spectrum. If the spectrum of a star is red or blue shifted, then it can be used to infer its velocity along the line of sight. Edwin Hubble observed that more distant galaxies tended to have more red shifted spectra. This establishes the theory of expansion of the universe. The lines in a star's spectrum is found to shift back and forth. What conclusion may be drawn from this observation?

A laser (light amplification by stimulated emission of radition ) provides a coherent (in phase) monochoramtic source of high intensity light . Lasers are used in eye surgery,CD/DV players basic research etc. Some modern eye lasers can be "tuned" to emit a desired wavelenght . The following table shows the lambda=(nm),v(s^(-1)) and E(J) but some of the date missing : [Take E(ev)=(1240)/lambda_(nm)] {:("Leser No.",lambda("nm"),v(s^(-1)),"Energy (J)"),("I",A,5xx10^(-14),B),("II",487.9,C,D),("III",E,F,3.2xx10^(-19)):} Which of the following statements(s) is /are correct? (i) All the three radiation (from laser ) lie in visble region (ii) The enegies D and B alone are not sufficient to remove electron completely from isolated gaseous H-atoms which is present at ground state (iii) In the spectrum the increasing order of lambda for the type of lasers is IIltIIIltI (iv) None of the above statement is correct

A metal foil is at a certain distance from an isotropic point source that emits energy at the rate P. Let us assume the classical physics to be applicable. The incident light energy will be absorbed continuously and smoothly. The electrons present in the foil soak up the energy incident on them. For simplicity , we can assume that the energy incident on a circular path of the foil with radius 5xx10^(-11) m (about that of a typical atom ) is absorbed by a single electron. The electron absorbs sufficient energy to break through the binding forces and comes out from the foil. By knowing the work function, we can calculate the time taken by an electron to come out i.e., we can find out the time taken by photoelectric emission to start. As you will see in the following questions, the time decay comes out to be large, which is not practically observed. The time lag is very small. Apparently, the electron does not have to soak up energy . It absorbs energy all at once in a single photon electron interaction. The experimental observations show that the waiting time for emission is 10^(-8) s. This observation contradicts the calculations based on classical physics view of light energy . Thus we have to assume that during photoelectron emission

Consider a gas consisting Li^(+2) (which is hydrogen like ion). (a) Find the wavelength of radiation required to excite the electron in Li^(++) from n=1 and n=3 . (Ionisation energy of the hydrogen atom equals 13.6 eV ). (b) How many spectral lines are observed in the emission spectrum of the above excited system?