Question

for an object placed at a distance 2 . 4 m from a lens, a sharp focused image is observed on a screen placed at a distance 12 cm from the lens. a glass plate of refractive index 1 . 5 and thickness 1 cm is introduced between lens and screen such that the glass plate plane faces parallel to the screen. by what distance should the object be shifted so that a sharp focused image is observed again on the screen?

Answer 1

To find the distance the object should be shifted, use the lens formula to calculate the initial and new image distances.

To find by what distance the object should be shifted so that a sharp focused image is observed again on the screen, we need to use the lens formula:

1/f = 1/v - 1/u

Where f is the focal length of the lens, v is the image distance, and u is the object distance.

Given that the screen is placed at a distance of 12 cm from the lens, and the object is initially placed at a distance of 2.4 m from the lens, we can calculate the initial image distance using the lens formula.

1/f = 1/v - 1/u

1/f = 1/12 - 1/2.4

Now, after introducing a glass plate of refractive index 1.5 and thickness 1 cm between the lens and the screen, the total distance between the lens and the screen becomes 13 cm. The distance between the object and the lens remains the same.

We can now use the new distances in the lens formula to find the new image distance:

1/f = 1/v - 1/u

1/f = 1/13 - 1/2.4

By comparing the initial and new image distances, we can determine the distance by which the object needs to be shifted to obtain a sharp focused image again on the screen.