angle of refraction at A if refractive index of the
material of the sphere is 3.
Air
A B
C
Air
60°
(b) When red light passing through a convex lens
is replaced by light of blue colour, how will the
focal length of the lens change?
OR
(a) Write the conditions under which light sources
can be said to be coherent.
(b) Why is it necessary to have coherent sources in
order to produce an interference pattern?
- (a) State the necessary conditions for producing
total internal re ection of light.
(b) Draw ray diagrams to show how specially
designed prisms make use of total internal
re ection to obtain inverted image of the object
by deviating rays (i) through 90° and (ii) through
180°.
SECTION C
- (a) A ray of light incident on
face AB of an equilateral
glass prism, shows minimum
deviation of 30°. Calculate
the speed of light through the
prism.
(b) Find the angle of incidence at face AB so that
the emergent ray grazes along the face AC.
- (a) An equiconvex lens of focal length ‘f’ is cut into
two identical plane convex lenses. How will the
power of each part be related to the focal length
of the original lens?
(b) A double convex lens of +5 D is made of glass
of refractive index 1.55 with both faces of equal
radii of curvature. Find the value of its radius
of curvature.
- Consider a plane e.m. wave travelling with speed c
in the positive z-direction.
(a) Use Faraday's law to show that E = cB
(b) Use modi ed Ampere's circuital law to show
that c=
∈
1
μ 00
A
B C
- Use Huygen’s principle to show how a plane
wavefront propagates from a denser to rarer
medium. Hence verify Snell’s law of refraction.
- Answer the following questions :
(a) In a double slit experiment using light of
wavelength 600 nm, the angular width of the
fringe formed on a distant screen is 0.1°. Find
the spacing between the two slits.
(b) Light of wavelength 500 Å propagating in air
gets partly re ected from the surface of water.
How will the wavelengths and frequencies of
the re ected and refracted light be a ected?
- Write Maxwell’s generalization of Ampere’s
Circuital Law. Show that in the process of charging
a capacitor, the current produced within the plates
of the capacitor is
i
d
dt
=ε φE
0
where φE is the electric ux produced during
charging of the capacitor plates.
- Suppose that the electric eld amplitude of an
electromagnetic wave is E 0 = 120 NC–1 and that its
frequency is X = 50.0 MHz.
(a) Determine, B 0 , Z, k and O.
(b) Find expressions for
E and
B.
- In the following diagram, an object ‘O’ is placed
15 cm in front of a convex lens L 1 of focal length 20
cm and the nal image is formed at I at a distance of
80 cm from the second lens L 2. Find the focal length
of the lens L 2.
P
15 cm
20 cm 80 cm
I
L 1
L 2
- An object of 3 cm height is placed at a distance
of 60 cm from a convex mirror of focal length
30 cm. Find the nature, position and size of the
image formed.
OR
(a) When the oscillating electric and magnetic fields
are along the x-and y-direction respectively.
(i) point out the direction of propagation of
electromagnetic wave.
