Title 4. OPTICS CW_KEY SOL..pdf ✅

IX– Physics (Vol – III) Olympiad Class Work Book 20. It is a case with plane mirror. The image is virtual of the same size and at the same distance at which the object lies. 21. The image always remains at far behind the mirror as the object is in front of him. Suppose the distance of the object from the mirror is x.Then distance of the object from the image will be 2x. So, when the man runs to wards the plane mirror at 1 vms , then the relative speed of image w.r.t him will be 2v i.e., 1 4ms . 22. There reflected ray turns through angle 2 , when the mirror is turned through angle  . Hence rotational speed of the light spot will be 2n revolutions per second.       speedof reflected light 2 r 2n 4 nr 23. Conceptual 24. 360 360 0 n 1 3 1 90                       25. R f and R 2    for plane mirror. 26. Subtract the given time from hr min 11: 60 . 27. 0 3 6 0 n 1 1 0 1 9 3 6      28. Mirror is rotated at angle 2 29. Reflected ray is rotated at angle 2 so o 40 30. Reflected ray is rotated at angle 2 so o 60 31. o o o o i 40 180 2i 180 2 40        WORKSHEET-2_KEY CUQ’S 1) 4 2) 1,3 3) 4 4) 1 5) 4 6) 2 7) 1 8) 2 9) 2 10) 3 11) 2 12) 2 JEE MAIN & ADVANCED 1) 4 2)2 3) 2 4) 2 5)4 6)1 7)3 8)4 9)2 10)2 11)3 12)4 13)2 14)2 15)3 16)a-2, b-1,c-3,d-4 17)4 18)1 19)4 20)4 21)1 22)4 23)1 24)3 25)4 26)4 27)2 SOLUTIONS: 1. R f 2  2. R 0.2 f 0.1m 2 2      3. 2 : 1
Olympiad Class Work Book IX – Physics (Vol – III) 4. C O F 10cm 15cm 30cm R = 40cm; f = –20cm u = –30cm 1 1 1 f v u   1 1 1 20 30 v     1 1 1 v 30 20   1 2 3 v 60   1 1 v 60   v 60cm   5. R f R 40cm 2    6. Virtual image formed is larger in size in case of concave mirror. 7. Here, object distance, u = -60cm Magnification, v m u   As the image is real v 1 u m or v 30cm u 2 2        