MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping
Menu
Shivam Bhagat Grade: 9
        . A ball is dropped from a height of 20 m above the surface of water in a lake. The refractive index of water is 4/3. A fish inside the lake, in the line of fall of the ball, is looking at the ball. At an instant, when the ball is 12.8 m above the water surface, the fish sees the speed of ball as 


(A) 9 m/s

(B) 12 m/s

(C) 16 m/s

(D) 21.33 m/s


7 years ago

Answers : (1)

vikas askiitian expert
510 Points
										

fish will see the image of ball after reraction through water surface...


using


             n2/v - n1/u = n2-n1/R


R for plane surface is infinity & n2(refrative index of water) , n1(refractive index of air)


         4/3v - 1/u = 0


         v = 4u/3  ..........1


now differentiating eq 1 wrt t


  (velocity of image)dv/dt = 4/3.(du/dt) (velocity of object)


now when ball has fallen 12.8m then its velocity is U..


 so velocity of ball as seen by fish is (4/3) .U


        V = 4/3. (U) =4/3 (sqrt2g(H-h))                                    (change in height (H-h) = 7.2m)


                          =4*12/3=16m/s

7 years ago
Think You Can Provide A Better Answer ?
Answer & Earn Cool Goodies
  • Complete Physics Course - Class 12
  • OFFERED PRICE: Rs. 2,756
  • View Details
  • Complete Physics Course - Class 11
  • OFFERED PRICE: Rs. 2,968
  • View Details

Ask Experts

Have any Question? Ask Experts

Post Question

 
 
Answer ‘n’ Earn
Attractive Gift
Vouchers
To Win!!! Click Here for details