7/26/2019 VISN1111-Tut3-2013

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VISN1111(2013) Week 4

VISN1111 Geometrical and Physical Optics 2013

Tutorial-3

1. For the purpose of calculation the eye may be considered as a single refracting surface

of +60 D power, having air one side and a medium of refractive index 4/3 on the other.

What must be the distance of the retina (the receiving screen) from this surface if the

eye is correctly focused on a distant object? What will be the distance of the object that

is focused by an eye in which the distance between the refracting surface and retina is

24mm?  Ans. 22.22 mm; − 22.5 cm 

2. Considering the eye as a single refracting surface of +5.56 mm radius of curvature,

having air on one side and a medium of refractive index 4/3 on the other, what will be

the size of the image formed of a distant object that subtends an angle of 1° at the eye?

 Ans. 0. 29 mm 

3. a) A spherical surface of radius +5 cm is polished on the end of a glass rod of refractive

index 1.550. Find its power when placed in (i) air, (ii) water of refractive index 1.333, (iii)

oil of refractive index 1.550 and (iv) liquid of refractive index1.650.

 b) A parallel pencil of monochromatic light enters the rod from the side with the index

stated in (i) to (iv) of part (a) of this question. Where will it focus in each case?

 Ans. (a) (i) +11 D (ii) +4.34 D, (iii) 0 D, (iv) −2 D

(b) (i) f ′ = +14.09 cm, (ii) f ′ = +35.71 cm (iii) +∞  (iv)  f ′ = −77.5 cm

4. A crown glass spherical surface (n′   =1.52) has a power of –10 D a) what is the surface’s

radius of curvature? b) What is the secondary focal length? c) What is the primary focallength?  Ans: -5.2 cm, -15.2 cm, 10 cm.

5. A crown glass spherical surface (n′   =1.52) has a radius of curvature of 15 cm. a) What is

the refractive power of the surface? b) What is the secondary focal length? c) What is the

 primary focal length?  Ans: 3.47 D, 43.8 cm, -28.82 cm. 

6. The pupil is located 3.6 mm from the cornea. Assume that the cornea has a radius of

curvature of 7.8 mm and the aqueous humor has an index of refraction of 1.333. How far

does the pupil appear to be from the cornea?  Ans: 3.06 mm 

7. A concave spherical surface separates water, nw = 1.333, and glass , ng = 1.533. Find the

location of the image of a point source in the water on the principal axis 1 m from the

surface if r  = −5 cm.  Ans. l′ = − 28.75 cm.

8. A spherical refracting surface, separating air from glass, forms a real image twice the size

of the real object. If the image is 6 times as far from F′ as the object is from F, find the

refractive index of the glass.  Ans. 1.5 

9. A glass paperweight (ng =1.53) has a picture fastened to its base. Its top surface is spherical

and has a radius of curvature of 50 mm, and its central thickness is 30 mm. Where will the

 picture appear to be when viewed through the top surface and what will be its linear

magnification?

 Ans. 24.75 mm below the top surface, 1.26  X