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Questions : #22 & #23 (In Hindi)
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In this lesson solve questions #22 & #23 from the question paper of IIT JEE MAINS 2017 - Set A

## Kumar Ketan is teaching live on Unacademy Plus

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3. IIT JEE 2017 PHYSICS Q. #1 to Q. #30 INDIAN IAN INSTITUTE Complete Paper Solution

4. Question 22 A diverging lens with magnitude of focal length 25 cm is placed at a distance of 15 cm from a converging lens of magnitude of focal length 20 cm. A beam of parallel light falls on the diverging lens. The final image formed is (1) Real and at a distance of 40 cm from convergent lens (2) Virtual and at a distance of 40 cm from convergent lens (3) Real and at a distance of 40 cm from the divergent lens (4) Real and at a distance of 6 cm from the convergent lens

5. f, 25 cm f 20 cm Sol 25 cm - -*--15cm For converging lens u-40 cm which is equal to 2f :. Image will be real and at a distance of 40 cm from convergent lens.

6. Question 23 In a Young's double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is (1) 1.56 mm (2) 7.8 mm (3) 9.75 mm (4) 15.6 mm

7. Sol. For For 2 .D 4 n X5 For

8. Question 24 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 A to after the collision is (1) 4A 1 (3) tA A =

9. m, + m 2 3 ,'' p1 = m. 2m,v m, + m2 4V . de-Broglie wavelength 2:1 B P

10. Question 25 Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths r X1/A 2, is given by E 4 (1) r 4/3 (2) r-2/3 (3) r 3/4 (4) r 1/3 -2 -3 E