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1. retina
sclera.........._
focal point
optic nerve
lens
cornea

)
pupil
iris
concave lens

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4. MIYOPIA INDRMAiL HYPERIMETR
1OPII.A

5. Ciliary
ffllllscles
retaxa:I~
fibers taut
lens at
minimum
strength for · .
distant
vlslt11.
The le ·\~e accoc11111,odt1tes
~
for clo}ie 1
1
i!fion by~
, tig/1ten;ng
rl1e ciliarJ'
1nu sci es, allo11
1i11g the
pliie1b
1
l1e cr)·stt1l/ine le11s
Ciliary
muscles
1COf1tracbJd.
fibers
slack. lens
rounds 10
greater
strength ror
close vision.
to f;eco,ne nltJre rc,1.111dell ..
Distant
Vision
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· · · Li:ght rays fronn1 distant
1objects are neart¥
paira1 lei and rdon1 need
as much refraction to
bring1 the,m to a focus.
Close
Vision
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lig'.ht. rays fr()ffl 01·ose
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require more
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oct1sing_

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Cross section or
human eye
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7. Pupil
Cornea -------
Anterior chamber -...­
(filled with
aqueous humor)
Posterior chamber
Suspensoryligaments
Ciliary
body and musde
----Eyelid
Tear duct
Vrtreous body
(filled with
vitreous
Lateral rectus musde
✓
a
---Choroid
,--Iii-..--Retina
Macola lutea
Fovea centralis
(central depression)
Optic nerve and
retinal blood vessels

8. ~~s:mi~B11~ ~tl~fi(@tillJ;IllJU'Jl• J 4
The Hum;in Eye• Colour of Obiects
• The rod ~d celli ol re-hna r•,pond to the intens.ity
of light. Le., the de&rff' of bri1htne~i o, darlt.ness but do
no1 re$pond to <olou~-
• The c~ ctill, air• i•n1itive to the d,fferent e•tent of
prima,y colOUfl M re-d. bAue and creeo.

9. The H uman Ev:<:• Colour of Obiects

10. CUSS 1
1
0
th
-PHYSICS -IME HUM'~N EYE ~ND _ 1 E C-OlfOORR!U! WORID
• Accomod."ltion·
➔ It 1, th• abUlty or the propetty of the eye lens 10 focus
both near and distant objecu by ~justin& ill f oc a4
lencth,
... However, the focal length c..-nnot " d~creased or
increased beyond a <ert•in limi14 du~ to which a he~thy
pen.on cannot view de:,rly. if th~ object is hefd too
dose (Le .• less 1hi1n 25 cm, or too fair from the eve.
➔ The ciU.ary mU$Clei ~Ip in ch.ln1ln1 the curvature of
thee~ l~ns..
... When mUS<Jes :w~ ,el~. the lens be- «>mM thin and
it$ focal lf-ngth ~ inc~.1~d-

11. The Hym:10 Eye• Terms Related to Hun1!)n ~
➔ Thk enables us to i~• di,t~nt objects cle~rfy.
➔ While vi~wing n•airby obje-cts. the Clllary muscles
Cortlrkt.
-+ So thct lens become t hkker and Its foc,il le-ngth
d•cr•~s..

12. Jhe Hum;,n EV'!,,• Term-s Related to Hum.1n E~
• Powe, o! Accom, 11od.1non:
➔ It Is th@ m.e,1 imum v~iation ir, power of eve tens for
focussi"I nt-1,y or f.tr obje<ts. < learlv at retin.-..
➔ For a youn1 ~duft with nc>ffl\al V,ision. th• pow•, of
atcommoct.wtion Is •~t 40.
-+ The eyt' loses Its pow~r of accommod.aaon at old ~t.
·-

13. The Human Eye -Terms Related to Human Eye
• Near point of the eye:
➔ The minimum distance, at which an object can be seen
most distinctly without any strain is called the least
distance
of the distinct vision.
➔ For a normal eye of an adult, it is 25 cm.
➔ It is also called near point of the eye.

14. The Human Eye -Terms Related to Human Eye
• Far point of the eye
➔ It is the farthest point up to which the eye can see
clearly.
➔ It is infinity for normal eye.
p
[~·e · ,; owu fa1· point
(:Xearer than infinity)
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15. Defects of Vision and their Corre ction
• The defects due to which a person cannot see the
object distinctly and comfortably are called defects of
vision.
• The main defects
of vision are:
1. Myopia
or near/short sightedness
2. Hypermetropia or far/long sightedness
3. Presbyopia

16. CLASS lOtti -PHYSICS -TAE AtlM~N EYE ~ND TRE COLOURFUL WOR
Defects of Vision and their Correction -Myopia
Myopia or Near/S hort Sightedness
• In this
defect, a person can see nearby objects distinctly but cannot see distant
objects clearly.
•
In this case, image formed before retina and not by retina.
Causes
• This
defect arises due to the decrease in focal length of the· lens because of
➔ Excessive curvature of eye lens
➔ Elongation of the eyeball
• As a result,
the image is formed before retina.

17. Defects of Vision and their Correction - Myopia
Remedy
• This
defect can be corrected by using concave lens.
• A concave lens
of suitable power will bring back the
image on retina.

18. Defects of Vision and their Correction -Hypermetropia
Hypermetropia
Correction: Convex lens

19. Defects of Vision and their Correction -Hypermetropia
Hypermetropia or Far/Long Sightedne ss
• In this defect, a person can see distant objects clearly but
cannot see nearby objects clearly.
• A person
with this defect has the near point farther away
from normal near point (25 cm).
• In this case, the image is formed behind retina.
Causes
• This
defect .arises due to following reasons:
➔ Focal length of eye lens becomes large.
➔ Eyeball becomes too short, so that the image is formed
behind retina.

20. Defects of Vision and their Correction - Hypermetropia
Remedy
• This
defect can be corrected by using a convex lens of suitable
power.
• This
will bring the image back on retina.

21. Defects of Vision and their Correction -Presbyopia
• It is found in old people.
• For most
of the people, the near point gradually recedes away
with age.
• Sometimes, a person may suffer
from both myopia and
hypermetropia.
Cau
ses
• This defect arises due to the following reasons:
➔ Weakness of ciliary muscles.
➔ Hardening or loss elasticity of eye lens.
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22. Daily Practice Questions
1. Colored part of the eye
a. Pupil
b. Iris
c. Corena
d. Sciera

23. CLASS' 10tt' -PHYSICS -THE HUMAN EYE AND :rHE COLOURFUL WORLD
Daily Practice Questions
2. Maximum refraction occurs at which part of eye.
a. Carena
b. Eye lens
c. Pupil
d. Retina

24. Daily Practice Qu estions
3. How does image formation at retina help in vision.
a. Due to presence of blind spot
b. Due
to presence of light sensitive cells
c. Due to less thickness of retina
d. All
of the above

25. Daily Practice Qu estions
4. Fluid chamber between eye lens and retina is filled with
a. Aqueous humor
b. Vitreous humor
C. Fats
d. All
of the above