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Questions : #45, #46 & #47 (In Hindi)
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In this lesson, questions #45, #46 & #47 are solved. Watch all the questions and keep practicing

Kumar Ketan is teaching live on Unacademy Plus

Kumar Ketan
#6 years teaching experience #Physics Faculty in Kota #"magical education" (200k+ subs) #Follow for Physics of JEE NEET AIIMS etc. #Writer

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mam plzz make a series on banking awareness mcq for ibps clerk......ty
Sakshi Pahwa
7 months ago
ok Shubham:)
sir question 47 mein jo concept use ho raha hai wo mujhe nhi pata can you plz help me in this matter from how can I get this concept
  1. ne

  2. 26.4k views 4.9 unacademy Kumar Ketan #16 Educator in IIT JEE #6 years teaching experience #IT JEE Physics #YouTuber (150k+ subs) #Unacademy educator(25kt lifetimeviews) #Under graduate topper Follow me on the Unacademy Learning App 1.3k 2 26 Followers Following Courses Get updates about new courses Watch all my lessons .Download slides and watch offline Lists (1) Kumar Ketan HINDI IIT JEE Physics by Kumar Ketan for lIT JEE 8 4 saves Kumar Ketan

  3. #Q.45 Light of wavelength 330 nm falling on a piece of metal eject electron with sufficient energy with required voltage V, to prevent them from reaching a collector. In the same set up, light of wavelength 220 nm ejects electron which require twice the voltage Vo to stop them reaching a collector. The numerical value of voltage Vois 16 15 15 15 16 b) d) 15

  4. Soln. hc hc 12 Subtracting Eq.(i) from Eq.(ii) Similarly, e(2%) (6.63x 10 )(3x10d10 1.6x10-19x330x220 10% >1.8 volt

  5. #Q.46 Maximum kinetic energy of photoelectron is E when the wavelength of incident light is 1. If energy becomes four times when wavelength is reduced to one-third, thern work-function of the metal is a) 3hc b) hc 3 hc d) 2- hc

  6. hc Soln Solving these equations, we get hc 31

  7. #Q.47 If the frequency of K X-ray emitted from the element with atomic number 31 is f, then the frequency of K X- ray emitted from the element with atomic number 51 would be b) 51f 31 a) 25f c) d) 25

  8. Soln. (2-1) for K-series Z2-1 51-1 31-1 25

  9. #Q.48 According to Moseley's law, the ratio of the slop of graph between /f and Z for Ks and Ka is 27 b) 32 32 a) 27 36 d) 5 36

  10. 2 1 2 slope oc 2 2 9 32 slope, slope2 2 2

  11. Soln.1 2 In 4 9 36 36 5R

  12. Soln. Energy of electron 10000eV 1500.122 (in A) 110000 , in A)-103030-12 10000