33.34.31.32.observed to be red shifted by 10Å. Find the speed
with which star is receding away from the earth.
(a) 5 10 /^5 m s (b) 10 /^5 m s(c) 100 /m s (d) 5 10 /^3 m s27.Two nicol prisms are kept perpendicular. One of
them is illuminated with a light intensity (natural)
I 0 .Two more nicol prisms are introduced in
between symmetrically. Find the light intensity
emitted from the last nicol prism.
(a)^027
128I
(b)^027
64I
(c)^09
64I
(d)^90
32I28.A slab consists of two parallel layers of copper
and brass of the same thickness and having thermal
conductivities in the ratio 1 : 4. The free end of
brass is at 100 C and that of copper at 0 .C the
temperature of interface is
(a) 20 C (b) 60 C (c) 40 C (d) 80 C
29.The temperature of the two outer surface of a
composite slab, consisting of two meterials having
coefficient of thermal conductivity K and 2K and
thickness x and 4x, respectively are
T 2 andT T1 2 1 T. The rate of heat transfer
through the slab, in a steady state
is 2 1
,A T T K
f
x
the value of f is(a)1
3
(b) 1 (c)2
3
(d)31.32.33.1 34.
2
A space object has the shape of a sphere of radius
R. Heat sources ensure that the heat evolution at a
constant rate is distributed uniformly over its
volume. The amount of heat liberated by a unit
surface area is proportional to the fourth power of
thermodynamic temperature. If the power liberated
is same and radius is made half of the initial value
then ratio of final temperature to initial temperatureis
(a) 2.19 (b) 0.414 (c) 1.414 (d) 4.
Forensic experts use Newton’s law of cooling to
find out when victim of crime died. They take the
temperature of the body when they find it and by
knowing the average temperature of the human
body. Initially and measuring the room temperature
they can find K and then t. Suppose that a body
was discovered at 12.00 PM in the midnight in a
motel room and its temperature was 80 .F The
temperature of the atmosphere is 60 .F Two hours
later the temperature of the body dropped to 75 .F
Find the time of death. (Assume that average
temperature of a living person is 98 )F
(a) 9:00 PM (b) 7:00PM
(c) 8:30PM (d) 7:30PM
A ray of light is incident at an angle i from denser
to rarer medium. The reflected and the refracted
rays are mutually perpendicular. The angle of
reflection and the angle of refraction are
respectively r and r', then the critical angle will
be(a) sin tan '^1 r (b) sin sin^1 r(c) tan sin^1 i (d) sin tan^1 iIf I 1 and I 2 be the size of the images respectively
for the two positions of lens in the displacement
method, then the size of the object is given by
(a) I1 2I (b) I1 2/I (c) I1 2/I (d) I1 2I
A prism of refractive index and angle A is
placed in the minimum deviation position. If the
angle of minimum deviation is A, then the value of
A in terms of is(a)
2cos^1
2
(b)
sin^1
2
(c)
cos^1
2
(d)^11
sin
2