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

Options

A. Only (iv)
B. (i)and(ii) only
C. (i),(ii)and(iii) only
D. (ii)and(iii) only

Answer

B

Explanation

(i) `Vlambda=C`
`lambda=(3xx10^(8))/(5xx10^(14))=6xx10^(-7)m`
`A=600nm`
`B=(1240)/(600)=2.06 eV=3.331xx10^(-19)J`
(ii) `D=(1240)/(487.9)=2.54 eV eV=4.07xx10^(-19)J`
(C) `c=(3xx10^(8))/(487.9)=10^(17) eV=6.148xx10^(14)sec^(-1)`
(iii) "Eengry" =`(3.2xx10^(-19))/(1.6xx10^(-19))=2 eV`
`E=lambda=(1240)/(2)=620 nm`
F=freq. = `(3xx10^(8))/(620xx10^(-19))=4.84xx10^(14)`
`D=2.5 eV`
Electron jumps from `2^(nd)` and `4^(th)` excited state by adsording energy equal to D