16. If f_b and f_g are the focal lengths of a convex lens for blue and red lights respectively and f_b and f_r are the respective value for a concave lens, then

1. 1. f_b > f_r and f_b > f_r

   
   
   

   2. f_b < f_r and f_b < f_r

   
   
   

   3. f_b > f_r and f_b < f_r

   
   
   

   4. None of these

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: B

   N/A

---

17. A real image is formed by a convex lens. If we put a concave lens in contact with it, the combination again forms areal image. The hew image

1. 1. Is closer to the lens system

   
   
   

   2. Is farther from the lens system

   
   
   

   3. Is at the original position

   
   
   

   4. None of the above

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: B

   N/A

---

---

18. Spherical aberration in a thin lens can be reduced by

1. 1. Using a monochromatic light

   
   
   

   2. Using a doublet combination

   
   
   

   3. Using a circular annular mark over the lens

   
   
   

   4. Increasing the size of the lens

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: C

   N/A

---

19. Glass has refractive index 3 / 2 and water has refractive index 4 / 3. If the speed of light in glass is 2.00 X 10⁸ m/s, the speed of light in water in m/s is

1. 1. 1.5 X 10⁸

   
   
   

   2. 1.78 X 10⁸

   
   
   

   3. 2.25 X 10⁸

   
   
   

   4. 2.67 X 10⁸

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: C

   N/A

---

---

20. Assertion (A) : In a motion picture usually 24 frames are projected every second over the whole length of the film
    Reason (R) : Am image formed on the retina of eye persists for about 0./s after the removal of stimulus.
    Codes:

1. 1. Both A and R are and R is the correct explanation of A

   
   
   

   2. Both A and R are true but R is not the correct explanation of A

   
   
   

   3. A is true but R is false

   
   
   

   4. A is false but R is true

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: C

   N/A

---