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ECAT Physics Chapter 19 Dawn of Modern Physics Online Test MCQs With Answers
Question # 1
Albert Einstein got the Nobel prize in physics for his explanation of photoelectric effect in
Choose an answer
1916
1919
1921
1923
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Question # 2
In order to produce pair production, a photon must have a energy
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0.511 Me v
0.256 Me v
1.02 Me v
0.956 Me v
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Question # 3
In the compton's effect, it is found that the wavelength of incident x-rays is
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greater than the wavelength of scattered x-rays
equal to the wavelength of scattered x-rays
less than the wavelength of scattered x-rays
any one of these
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Question # 4
The threshold frequency of sodium is 6 x 10
6
MHz. The cut-off wavelength for this metal will be
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500 m
500 nm
500 km
500 cm
None of these
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Question # 5
A black body is
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an ideal absorber
an ideal radiator
both of them
none of them
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Question # 6
Converse of pair production is known as
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Compton effect
annihilation of matter
photoelectric effect
none of these
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Question # 7
The value of threshold frequency for different metals is
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different
same
may be different or may be same
none of these
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Question # 8
Compton derived an expression to find compton shift by applying to the process, the law of conservation of:
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Energy only
Momentum only
Mass only
Charge only
Both (A) and (B)
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Question # 9
The energy of a photon in a beam of infrared radiation of wavelength 1240 nm is
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100 ev
10
6
e v
10
3
e v
1.0 e v
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Question # 10
When platinum wire is heated, then at the temperature of 500
o
C, it becomes:
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Yellow
Orange red
Dull red
White
Cherry red
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Question # 11
When the atomic particle are moving with velocities approaching that of light:
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Newton's laws become valid
Relativistic effects become prominent
Botha(A) and (B) are valid
Neither (A)nor (B)
There mass becomes zero.
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Question # 12
If you are moving at relativistic speed between two points that are a fixed distance apart, then the distance between the two points appers
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larger
shorter
equal
none of these
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Question # 13
If the radius of first orbit of hydrogen atom is 0.53
° A the radius of second orbit will be
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2.120
°A
0.212
°A
21.2
°A
0.14
°
a
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Question # 14
There is no way to detect:
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Absolute uniform motion
Accelerated motion
State rest
State of motion
None of these
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Question # 15
If A represents linear momentum and c, the velocity of light, then unit of pc in international system of units is:
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Newton
Joule
Joule-Sec
Joule-s
-1
Watt
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Question # 16
S.I. unit of planks constant is
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J-s
-1
J.s
J.s
-2
J.s
2
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