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UNIT
5: GEOMETRIC OPTICS
 5.1
Reflection of light at plane surfaces.
(6 Periods)
 Regular and diffuse
reflection.
Rotation of a plane
mirror with direction of incident ray.
Images formed in
a plane mirror.
Focal point, focal
length, centre of curvature.
Assessment objectives
By the end of this topic, the student should be
able to:
- Define a ray of light.
- Define a beam of light and draw sketch diagrams
for the convergent and
divergent beams.
- Perform and describe an experiment to illustrate
the principle of reversibility
of light.
- State the laws of reflection of light.
- Perform and desctibe an experiment to illustrate
the laws of reflection of
light.
- Distinguish between regular an diffuse refleciton.
- Perform and describe an experiment to determine the
relation between angle
of rotation of a plane mirror and angle of the reflected
ray while keeping the
direction of the incident ray fixed.
- Describe the application of rotation of a plane mirror
in the light beam galvanometer.
- Perform and describe an experiment to find the position
and nature of an image formed
by a plane mirror.
- Derive and use the expression relating the number
of images formed by two inclined
mirrors and the angle between the two mirrors.
- List uses of plane mirrors.
5.2
Reflection of light at curved surfaces.
(9 Periods)
The equation
1 + 1 = 1 = 2
u v f
r
Spherical aberration,
caustic surface.
Assessment objectives
By the end of this topic, the student should be
able to:
- Describe the types of curved mirrors.
- Define the terms focal point, centre of curvature,
radius of curvature,
pole and aperure as applied to curved mirrors.
- Derive and use the relation r = 2f for
curved mirrors.
- Distingiush between marginal and paraxial rays.
- Describe the formation of caustic surface.
- Describe spherical aberration and the use of parabolic
mirrors to
- correct the defect.
Derive and use the formula 1 + 1 =
1 = 2
u v f
r
- Determine image and object position, focal length
and radius of curvature
by construction and calculation.
- Distinguish between the nature of images formed by
convex and concave mirrors.
- Perform and describe experiments to detemine focal
length or radius of curvature
of curved mirrors.
- Perform and describe experiments to determine focal
length or radius of curvature
of curved mirrors using a distant object, no-parallax
and an illuminated object.
- List applications of concave and convex mirrors.
5.3
Refraction of light at plane boundaries
(9 Periods)
Snell's law.
Real and apparent
depth.
Critical angle
and total internal reflection.
- applications, including optical fibres.
Assessment objectives
By the end of this topic, the student should be
able to:
- Perform and describe experiments to demonstrate refraction
of light through
a glass block and through a liquid.
- State the laws of refraction.
- Perform and describe an experiment to establish
sin i = constant
sin r
- Define refractive index and explain its variation
with optical media.
- Define refractive index in terms of velocities of
light in the respective media.
- Derive and use relation gna
= 1
ang
- Derive and use the the expression 1n3
= 1n2 x 2n3
for three parallel sided
transparent media.
- Derive and use the expression n sini = constant.
- Perform and describe an experiment to determine the
refractive index by the
apparent depth method.
- Explain critical angle and the total internal reflection.
- State the conditions for the occurence of total internal
reflection.
- List applications of total internal reflection e.g
fibre optics, radio wave transmission,
binoculars, periscopes and mirage formation.
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