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Questions : #21, #22, #23 & #24 (In Hindi)
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In this lesson we'll solve questions #21, #22, #23 & #24 from MODERN PHYSICS for IIT JEE MAINS and ADVANCE

## Kumar Ketan is teaching live on Unacademy Plus

Kumar Ketan
#Specialisation in Electronics #6 years teaching experience #Physics Faculty in Kota #"magical education" (231k+ subs) #Writer

U
sir balmer k lie longest wavelength kya ayegi?
sir q.21me doubly ionized lithium ka matlab kya hua
Kumar Ketan
a year ago
An element, z=3 and it has only one electron like hydrogen
1. ne

3. #200 Most Important Questions of Modern Physics for IJT JEE MAINS and ADVANCE Electron Beam Dissociative Result Fiber 2e. Precursor Mirror Charged and Neutral Fragments Light source Non-dissociative Result ivot Parent Molecule Scale lonized Parent Molecule

4. #Q.21 The frequency of first line is Lyman series in the hydrogen spectrum is v. What is the frequency of the corresponding line in the spectrum of doubly ionized Lithium? b) 3v d) 2v a) V c) 9v

5. Frequency cEnergy and Energy x z2

6. #Q.22 Which energy state of doubly ionized Lithium (Li") has the same energy as that of the ground state of hydrogen ? a) n1 c) n-3

7. SolnE oc

8. #Q23 An electron is accelerated by potential difference of 25 volt. Find the de-Broglie wavelength associated with it. Solution For an electron, de-Broglie wavelength is given by 150150 VV25 6 2.5 A

9. #Q.24 The longest wavelength of Lyman series for hydrogen atom is the same as the wavelength of certain line in the spectrum of He when the electron makes a transition from n->2. The value of n is a) 3 c) 5 b) 4 d) 6

10. Soln. Longest wavelength of Lyman series means, minimum energy corresponding n-2 to n=1 13.6 13.6- 13.6(Z): 13.6(Z)2 2 Putting Z-2, we get n-4

11. Sol. For K, line,ni-1 and n2 -2 -1.0973 107x(91x91)(H)

12. #Q.28 If E,,E, and E, respectively the kinetic energies of an electron, an a -particle and a proton each having same de-Broglie wavelength, then b) E2>E,>E

13. V2Em where , h and E are constant. So,