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Questions : #6(JEE-2017), #7(JEE-2017) & #8(JEE-2018) (In Hindi)
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In this lesson solve questions #6, #7 & #8 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" (211k+ subs) #Writer

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thanku sir
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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.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

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

6. #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

7. Sol. From energy level diagram hc hc 3

8. #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

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

10. #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

11. #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

12. h211hc hc 2m 2m 2,2