Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
126 views
in Physics by (87.1k points)
closed by
(a) A normal eye has retina `2cm` behind the eye lens. What is the power of the eye lens ehen the eye is (i) fully relaxed, (ii) most strained ?
(b) The near point and the far point of a hild are at `10cm` and `100cm`. If the retain is `2.0cm` behind the eye lens, what is the range of the power of the eye lens?
(c) A young boy can adjust the power of his eye lens between `50D` and `60D`. His fat point is infinity. (i) what is the distance of his retina from the ye lens? (ii) What is near point?

1 Answer

0 votes
by (84.5k points)
selected by
 
Best answer
(a) (i) image
`u = oo, v = 2cm`
`(1)/(v)-(1)/(u)=(1)/(f) rArr f = v = 2cm`
`P = (100)/(f(cm)) = (100)/(2) = 50D`
(ii) image
`(1)/(f)=(1)/(v)-(1)/(u)=(1)/(2)-(1)/(-25) = (17)/(50) rArr f = 50//27`
`P = (100)/(f(cm)) = (100)/(50//27) = 54D`
(b) image
`(1)/(f)=(1)/(v)-(1)/(u)=(1)/(2)-(1)/(-100)=(50+1)/(100)=(51)/(100) rArr f=(100)/(51)cm`
`P = (100)/(f(cm)) =(100)/(100//51) = 51D`
image
`(1)/(f)=(1)/(v)-(1)/(u)=(1)/(2)-(1)/(-10)=(6)/(10) rArr f = (10)/(6)=(5)/(3)cm`
`P = (100)/(f(cm)) = (100)/(5//3) = 60D`
Range: `51D` to `60D`
(c) when the eye is most relaxed, focal length is maximum or power is minimum hence in most relaxed case, `P = 50D`,
`f = (100)/(P)=(100)/(50) = 2cm`. The rays coming from infinite are focused at retina, hence `v = 2 cm = f`
image
`(1)/(v)-(1)/(u)=(1)/(f) rArr (1)/(v)-(1)/(oo)=(1)/(2) rArr v = 2cm`
Distance of retina from lens `d =v=2cm`
The eye is most strained when object is at near point. Hence focal length is minimum or power is maximum i.e `60 D`,
`f = (100)/(60) = (5)/(3)cm`. The image is formed at retina.
image
`(1)/(v)-(1)/(u)=(1)/(f)`
`(1)/(2)-(1)/(u)=(1)/(5//3) rArr (1)/(u)=(1)/(2)-(3)/(5)=(5-6)/(10) rArr u =- 10cm`
`N.P. = 10cm`

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...