Geometrical and Waves Optics (PHYS2203)
BSc, Physics - PHYS
Semester: Second Semester
Level: 200
Year: 2018
REPUBLIC OF CAMEROON THE UNIVERSITY OF BAMENDA
Peace-Work-Fatherland P.O BOX 39 Bambili
School/Faculty: Science Department: Physics Lecturer(s): Dr. Zambo/ Mr. Assembe
Course Code: PHYS2203 Course Title: Geometric and Wave Optics
Date: 10/07/2018 Hall: PBB06 Time: 14H30-17H30
Instructions: Answer all questions showing all detailed calculations
QUESTION 1(4 Marks)
Assuming that the end points A and B of the travel path followed by a ray-light are fixed, show that
the optical path from A to B is unique under the Fermat’s principle and derive the Snell’s laws for
refraction, for a ray travelling across any transparent surface separating two media of different
refractive indices.
QUESTION 2(6 Marks)
We consider a system of two parallel plane dioptres bounding a medium of index n=1.55 and
thickness e=20 mm. we assume that the two external media to the system of dioptres is identical.
1. Determine the deviation d of the refracted ray across the upper surface from the incident
ray, within the medium of index n. ……………………………………………………………….[2 marks]
2. Show that the transmitted ray emerges across the lower surface parallel to the incident
ray…………………………………………………………………………………………………………………..[2 marks]
3. Find the condition for which a reflection will rather occur at the lower surface instead of
refraction as previously studied. ……………………………………………………………………..[2 marks]
QUESTION 3(10 Marks)
Following a meridional ray through a spherical refracting surface of radius R= 55cm, centred at C
that separates two media of respective index n1 and n2(n1=1 and n2=1.5).
A ray leaves a point A located at a distance D from the vertex V of a spherical surface, then it
intersects the optical axis at O, crosses the surface at P and intersects the optical axis again at I. we
consider 1, 2, I and r are respectively, angles of inclination with the optical axis before and after
the refraction, the angle of incidence and the angle of refraction. h=10 cm is the elevation of the ray
from the optical axis at A and 1 = 20°.
1. Define meridional ray and give the nature of the pair of points (O,I). [2 marks]
2. Draw a clean and neat diagram using the scale 1/10 for the distance. [2 marks]
3. Determine D, if the ray cuts the axis 52.5 cm from the vertex [2 marks]
4. Find the incident angle i. deduct the angle of refraction r. [2 mark]
5. Determine angle 2 at which the refracted ray intersects the optical axis and the D’ distance
from the vertex to the point I.
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