5.4 Refraction through Prisms (9
periods)
 Minimum deviation
Deviation by thin
prisms.
Prism spectrometer
and white light spectrum.
Assessment objectives
By the end of this topic, the student should be
able to:
- Explain dispersion of white light by a prism.
- Derive and use the expression for deviation
d = ( i1 - r1) + (i2
- r2)
- Derive and use the expression d = ( n - 1)A
for a small angled prism.
- State conditions required for minimum deviation to
occur.
- Derive and use the expression n = sin(A+Dmin)
/ sin A
2
2
- Perform and describe experiments to measure angle
A of
a prism and Dmin using a spectrometer.
- Perform an experiment to determine refractive index
of the material of the prism
using optical pins and spectrometer.
- Describe applications of glass prisms.
5.5
Refraction through a thin lens. (12
Periods)
Types of lenses.
Focal points, focal
lengths
Power of lens.
Thin lens formula
1 + 1 = 1
u v
f
Transverse magnification.
Displacement formula,
L2-d2 = 4d¦
Conjugate foci;
Newton's formula xy =¦2
Full lens formula
1 = (n-1) ( 1 + 1 ) for a thin
lens in air.
¦
r1 r2
Methods of determination
of focal lengths of both converging and
diverging lenses.
Defects of images
formed by a lens;
- spherical and chromatic aberration.
Assessment objectives
By the end of this topic, the student should be
able to:
- Identify converging and diverging lenses.
- Define the terms:- principle focus, principle axis,
optical centre,
focal length as applied to converging and diverging lenses.
- Draw ray diagrams to illustrate formation of real
and virtual images.
- Derive and use the expression 1
+ 1 = 1 = 2
u v
f r
- Define transverse magnification.
- Derive and use the relation: m =
v
u
- Derive and use the expression L2 -
d2 = 4d¦
- Derive and use the expression 1
= 1 + 1 for thin
lenses in contact.
F ¦1
¦2
- Define power of the lens and state its units.
- Derive and use Newton's formula xy =¦2
- Derive and use the expression 1
= ( n - 1) ( 1 + 1 )
- Explain chromatic aberration and spherical aberration
in lenses and how
they are minimised.
- Perform an experiment to demostrate chromatic aberration
and spherical
aberration in lenses.
- Perform and describe experiments to determine focal
length and radii of the
surfaces of the lenses.
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