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ECAT Physics Chapter 19 Dawn of Modern Physics Online Test MCQs With Answers
Question # 1
A black body is
Choose an answer
an ideal absorber
an ideal radiator
both of them
none of them
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Question # 2
Which of the following is not an example of intertial frame
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a body placed on the surface of earth
a body placed in a car moving with uniform velocity
a body placed in a car moving with same acceleration
none of these
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Question # 3
According to Einstein, with the great increase in the speed of the body, the relativistic mass of the body
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Remains constant
Decreases
Increases to infinity
Reduced to zero
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Question # 4
A non-inertial frame of reference is one, in which
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law of inertial is valid
all laws of physics are the same in all frames
a>0 or a<0
a=0
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Question # 5
Position and momentum of a particle cannot both be measured simultaneously with perfect accuracy. This is the statement of
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photoelectric effect
pair production
Compton effect
uncertainty principle
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Question # 6
An electron is accelerated through a potential difference of 50v. its de-Brogile wavelength is
Choose an answer
1.66 x 10
-29
m
1.74 x 10
-10
cm
17.4 x 10
-6
m
1.74 x 10
-10
m
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Question # 7
When low energy photon interact with a metal,which of the following effect is likely to be taken place
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pair production
photoelectric
Compton effect
None of these
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Question # 8
When a platinum wire is heated, it appears yellow at
Choose an answer
1600°C
900°C
1100°C
1300°C
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Question # 9
In photoelectric effect the energy of ejected electrons depend on
Choose an answer
The frequency
The intensity
Both frequency and intensity
None of these
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Question # 10
The energy of the 4th orbit in hydrogen atom is
Choose an answer
2.5 ev
- 3.5 ev
-0.85 ev
-13.6 ev
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Question # 11
In process of annihilation of matter, the two photons produced move in opposite direction to converse
Choose an answer
momentum
charge
energy
mass
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Question # 12
As compared to the distance measured by an observer on Earth, the distance from Earth to a star measured by an observer in a moving spaceship would seem:
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Smaller
Lerger
Same
Much larger
None of these
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Question # 13
The mass of an object will be doubled at speed
Choose an answer
1.6 x 10
8
ms
-1
2.6 X 10
8
ms
-1
2.6 x 10
7
ms
-1
2.6 x 10
9
ms
-1
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Question # 14
The value of the Stephen's constant for black body radiations is given by
Choose an answer
5.6 x 10
8
Wm
-2
K
-4
5.67 x 10
-8
Wm
-2
K
-4
2.9 x 10
-3
mK
2.9 x 10
3
mK
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Question # 15
The location and speed anywhere on earth can now be determined using relativistic effects by NAVISTAR to an accuracy of
Choose an answer
2 cm/s
20 cm/s
200 cm/s
2000 cm/s
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