Geometrical Optics - Kar

146 Pages·2013·1.72 MB·English

PHYSICS
Geometrical Optics
Presented by
Kusagatti T A
PHYSICS
Q 1 : Let the x-y plane be the
.(AIEEE 2011)
boundary between two transparent
media. Medium 1 in z ≥ 0 has a
refractive index of √2 and medium 2
with z < 0 has a refractive index of
√3. A ray of light in medium 1 given
by the vector A = 6√3i +8√3j -10k is
incident on the plane of separation.
The angle of refraction in medium 2
is? a)45o
b)60o
c)75o
d)30o
PHYSICS
Sol.1: ray is A = 6√3i +8√3j -10k
H ere x-y plane is boundary between two
media.

cos i = |[OZ/√Ax2+Ay2+Az2]|

= [10/ √36x3+64x3+100
=10/ √400

= ½
→ i =600
From Snell’s law
sin i / sin r = √3/√ 2
r = 45O
Ans (a)
PHYSICS
Q 2. A ray of light traveling in water is incident
on its surface open to air. The angle of
incidence is θ, which is less than the critical
angle. Then there will be
a)Only reflected ray and no refracted ray
b)Only a refracted ray and no reflected ray
c) A reflected ray and a refracted ray and the
angle between them would be less than 180-
2θ
d)A reflected ray and a refracted ray and the
angle between them would be greater than
180-2θ
PHYSICS
Sol.2:
L ight is traveling from denser to rarer
medium i.e. r > θ
X+r+ θ =180

X = 180 – r – θ

X < 180 - 2 θ |since r > θ

Ans (C)
PHYSICS
Q.3 : A ball is dropped from
(IIT – JEE 2009)
a height of 20 m above the surface
of water in a lake. The refractive
index of water is 4/3. A fish inside
the lake, in the line of fall of the
ball, is looking at the ball. At an
instant, when the ball is 12.8 m
above the water surface, the fish
sees the speed of ball as
(a) 9 ms-1
(b) 12 ms-1
(c) 16 ms-1
(d) 21.33 ms-1
PHYSICS
Sol.3 For freely falling body v2 =u2 +2gh

Ans = (c)
PHYSICS
Q.4. A light ray traveling in a
(IIT-2011)
glass medium is incident on a glass

–air interface at an angle of
in cidence θ. The reflected (R) and
transmitted (T) intensities, both as
function of θ, are plotted. The
correct sketch is
PHYSICS
Sol.4
If the angle of incidence is greater than
critical angle, no light is transmitted.

Hence intensity of transmitted light

become zero.

If Ө<C, maximum light is transmitted.
And very little light is reflected

Ans = ( c )
PHYSICS
Q.5. A ray OP of monochromatic
(IIT-2010)
light is incident on the face AB of prism
ABCD near vertex B at an incident angle
of 600. If the refractive index of the
material of the prism is√3, which of the
following is (are) correct?

(a)The ray gets totally internally
reflected at face CD
(b) The ray comes out through face AD
(c) The angle between the incident ray
and the emergent ray is 1200
(d)all the above