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ECAT Pre General Science Physics Chapter 19 Dawn of Modern Physics Online Test MCQs With Answers
Question # 1
Practically the quantity v/c is always:
Choose an answer
less than one
Equal to one
Greater then one
all of these
None of these
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Question # 2
According to Einstein, with the great increase in the speed of the body the relativistic length of the body
Choose an answer
Remains constant
Decreases
Increases
Reduces to zero
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Question # 3
Intensity of light determines the:
Choose an answer
Energy of each photon
Number of photons
Speed of photons
Size of photons
None of these
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Question # 4
According to the special theory of relativity, time is
Choose an answer
absolute quantity
not absolute quantity
constant quantity
none of these
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Question # 5
The emission of electrons from a metal surface when exposed to light of suitable frequency is called the
Choose an answer
pair production
Compton effect
photoelectric effect
relativity
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Question # 6
The Einstein's changes in length, mass and time are not observed in common life because
Choose an answer
We dont observer then seriously
The masses are too large
Their speed is too small than the speed of right
All of the above
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Question # 7
According to Einstein, with the great increase in the speed of the body, the relativistic mass of the body
Choose an answer
Remains constant
Decreases
Increases to infinity
Reduced to zero
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Question # 8
The general theory of relativity treats problems involving
Choose an answer
inertial frame of references
accelerating frame of references
both of these
none of these
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Question # 9
The mass 'm' of a body moving at 0.8 c (whose rest mass is mo) becomes
Choose an answer
2 mo
1.67 mo
0.67 mo
2.67 mo
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Question # 10
When platinum wire is heated, then at the temperature of 500
o
C, it becomes:
Choose an answer
Yellow
Orange red
Dull red
White
Cherry red
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Question # 11
Which of the following phenomenon proves the particle nature of light
Choose an answer
interference
diffraction
photoelectric effect
none of these
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Question # 12
Photoelectric effect takes place with a photon of:
Choose an answer
Very high energy
Very low energy
Low energy
High energy
None of these
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Question # 13
The intensity of emitted energy (with wavelength) radiated from a black body at different temperatures was initially measured by:
Choose an answer
Lummer
Planck
Pringsheim
Both (A ) and (B)
Both (A) and (C)
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Question # 14
A non-inertial frame of reference is one, in which
Choose an answer
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 # 15
The energy of a photon in a beam of infrared radiation of wavelength 1240 nm is
Choose an answer
100 ev
10
6
e v
10
3
e v
1.0 e v
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Question # 16
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 # 17
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 # 18
Wave nature of particle was proposed by
Choose an answer
Einstein
Plank
De-Brogile
Max well
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Question # 19
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:
Choose an answer
Smaller
Lerger
Same
Much larger
None of these
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Question # 20
According to the electromagnetic wave theory of light, increasing the intensity of incident light should increase the
Choose an answer
number of photoelectrons
size of the photoelectrons
charge on photoelectrons
K.E of photoelectrons
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Question # 21
Electromagnetic -radiation means:
Choose an answer
Photons
protons
Electrons
Mesons
None of these
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Question # 22
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 # 23
The analysis of the distribution of wavelengths of the radiation emitted from a hot body set the foundation of new mechanics, known as
Choose an answer
classical mechanics
Newtonian mechanics
quantum mechanics
statistical mechanics
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Question # 24
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 # 25
Photoelectrons are emitted when ultraviolet light falls on:
Choose an answer
Casium
Silver
Potassium
Any of these
None of these
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Question # 26
When a platinum wire is heated, it appears white at
Choose an answer
1600
°C
900
°C
1100
°C
1300
°C
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Question # 27
The special theory of relativity is based on:
Choose an answer
Four postulates
Three postulates
Two postulates
One postulate
None of these
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Question # 28
Current, voltage, resistance measuring circuit is connected with the galvanometer with the help of switch, known as
Choose an answer
ON switch
off switch
function switch
none of these
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Question # 29
A particle having mass and charge equal to that of an electron is called:
Choose an answer
Proton
Positron
Pion
Pi-meson
Both (C) and (D)
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Question # 30
The threshold frequency of sodium is 6 x 10
6
MHz. The cut-off wavelength for this metal will be
Choose an answer
500 m
500 nm
500 km
500 cm
None of these
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Question # 31
The photoelectric effect, the maximum energy of photoelectrons depends on the
Choose an answer
particular metal surface
frequency of incident light
both of them
none of them
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