Try the new Google Books
Check out the new look and enjoy easier access to your favorite features
Page 2
Answer
Text Solution
Answer : The prescribed lens is convex lens of focal length +0.67 m and the defect in vision is hypermetropia (farsightedness).
Solution : Given: Power (P) =+1.5 D <br> To find: Focal length (f) <br> Formula: `P=(1)/(f(m))` <br> Calculation: From formula, <br> `f=(1.5)=+0.67 m` <br> The prescribed lens is convex lens as the focal length is positive. Convex lens has positive focal length and it is used for the correction of farsightedness or hypermetropia. Thus, the defect in vision is hypermetropia (farsightedness).
Given
P = +1.5 D
Find out
We need to find out the focal length of the given lens
Solution
We know that
f = 1/P
Where,
f is the focal length
P is power
f = 1/P
= 1/+1.5 = 0.67 m.
As the power of the lens is (+ve), the lens is converging.
Was this answer helpful?
4 (139)
Thank you. Your Feedback will Help us Serve you better.
Solve the following example.
Doctor has prescribed a lens having power +1.5 D. What will be the focal length of the lens? What is the type of the lens and what must be the defect of vision?
Given:Power of lens, P = +1.5 DNow, focal length of lens, \[f = \frac{1}{P} = + \frac{1}{1 . 5} = + 0 . 67 m\]Since, the focal length is positive, the lens prescribed for correction is convex lens. Thus, the defect of vision is farsightedness or hypermetropia.
Concept: Eye Defect and its correction: Hypermetropia or far-sightedness
Is there an error in this question or solution?