Let’s determine what lens is needed to correct the vision of a myopic eye. Assume that the far point of the myopic eye is 50 cmcm in front of the eye. What lens should be used to focus sharply on an object at infinity? (Assume that the distance from the lens to the eye is negligible.)

Explanation:

Person suffering from myopia is unable to see objects beyond 50 cm  because far point of his vision is 50 cm . He requires a concave lens

( diverging lens ) to correct his vision .

After using the lens ,

ray of light coming from far off place will appear to be coming from 50 cm after refraction through lens so it will be focused on retina .

object distance u = ∝

image distance v =  - 50 cm

focal length f = ?

1 / v - 1 / u = 1 /f

- 1 / 50 - 1 / ∝ = 1 / f

- 1 / 50  = 1 / f

f = - 50 cm

focal length is negative so len is concave.

He requires  concave lens of focal length 50 cm .

c. newton's third law of motion

c. magnitude and direction