## Kumar Ketan is teaching live on Unacademy Plus

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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

#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

#Q.6. : An electron beam is accelerated by a potential difference V to hit a metallic target to produce X-rays. It produces continuous as well as characteristic X-rays. If Amin is the smallest possible wavelength of X- ray in the spectrum, the variation of log min with log V is correctly represented in (1) log (2) log log V log V (3) log (4) log log V

Sol. In X-ray tube hc eV min hc Slope is negative Intercept on y-axis is positive log in log V

#Q.7. : Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths r -A 1/A2, is given by (1) r 4/3 (2) r-2/3 (3) r 3/4 (4) r = 1/3 4 3 3E

Sol. From energy level diagram hc hc 3

#0.8. : If the series limit frequency of the Lyman series is VL, then the series limit frequency of the Pfund series is (1) 25 v (2) 16 v (3) v/16 (4) v25

Sol, hv, = E |- 1 E L52 00 -25 25

#Q.9. : A particle A of mass m and initial velocity v collides with a particle B of mass m/2 which is at rest. The collision is head on, and elastic. The ratio of the de-Broglie wavelengths t 4x after the collision is (1) 4-1 3 (3) A 2 3 (2) = 2 (4) 4- 2

#Q.10. : from n-5 state to n-1state is m/s. Solution From conservation of linear momentum, |Momentum of recoil hydrogen atomI |Momentum of emitted photon l The recoil speed of a hydrogen atom after it emits a photon is going (JEE 1997) or Here, 52 1 (13.6) (24/25) eV 13.056 eV -13056 x 1.6 x 10-19 J-2.09 x 10-18 J m - mass of hydrogen atom - 1.67 x 10-27kg 2.098 10-18 an AE mc (1.67 x1027) (3 x108) v- 4.17 m/s

h211hc hc 2m 2m 2,2