# An object is at a distance of 20m from a convex lens of focal length 0.3 m. The lens forms an image of the object. If the object moves away from the lens at a speed of 5 m/s, the speed and direction of the image will be : (a) 0.92×10−3 m/s away from the lens (b) 2.26×10−3 m/s away from the lens (c) 1.16×10−3 m/s towards the lens (d) 3.22×10−3 m/s towards the lens

## Question ID - 50315 :- An object is at a distance of 20m from a convex lens of focal length 0.3 m. The lens forms an image of the object. If the object moves away from the lens at a speed of 5 m/s, the speed and direction of the image will be : (a) 0.92×10−3 m/s away from the lens (b) 2.26×10−3 m/s away from the lens (c) 1.16×10−3 m/s towards the lens (d) 3.22×10−3 m/s towards the lens

3537

From lens equation    m= Velocity of image w.r.t to lens is given by VI/Lm2V O/L

direction of velocity of images is same as that of object

VO/L=5 m/s

VI/L= (5)

=1.16×103 m/s towards the lens

Next Question :
 A body of mass 1 kg falls freely from lens of 100 m on a platform of mass 3 kg which is mounted on a spring having spring constant K=1.25×106 N/m. The body sticks to the platform and the spring’s maximum compression is found to be x. Given that g=10ms−2, the value of x will be close to (a) 4 cm (b) 8 cm (c) 80 cm (d) 40 cm 