More Classes
5th Class
6th Class
7th Class
8th Class
9th Class
10th Class
11th Class
12th Class
NAT I
NAT II
CSS
IQ
General Knowledge
MDCAT
ECAT
GAT General
GAT Subject
Other Links
Go to Home
Online Tests
ECAT Pre General Science Physics Chapter 19 Dawn of Modern Physics Online Test MCQs With Answers
Question # 1
The Stephen-Boltzmann law for the black body radiation is given by
Choose an answer
E = T
2
E = -T
2
E = T
4
E = -T
4
Previous
Skip
Next
Question # 2
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
Previous
Skip
Next
Question # 3
Photoelectrons are emitted when ultraviolet light falls on:
Choose an answer
Casium
Silver
Potassium
Any of these
None of these
Previous
Skip
Next
Question # 4
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
Previous
Skip
Next
Question # 5
The length contraction happens only
Choose an answer
Opposite to the direction of motion
along the direction of motion
perpendicular to the direction of motion
In any direction
Previous
Skip
Next
Question # 6
Max plank received the Nobel Prize in physics for his discovery of energy quanta in
Choose an answer
1900
1906
1912
1918
Previous
Skip
Next
Question # 7
The photon of radio-waves has energy of about
Choose an answer
1 Me V
1 Ke v
10
-10
e v
10
10
e v
Previous
Skip
Next
Question # 8
Victor de-Brogile received the Nobel prize in physics in
Choose an answer
1925
1929
1932
1935
Previous
Skip
Next
Question # 9
S.I. unit of planks constant is
Choose an answer
J-s
-1
J.s
J.s
-2
J.s
2
Previous
Skip
Next
Question # 10
The way through which electromagnetic radiations or photons interact with matter depends upon their:
Choose an answer
Wavelength
Frequency
Energy
Temperature
All of these
Previous
Skip
Next
Question # 11
The special theory of relativity is based on:
Choose an answer
Four postulates
Three postulates
Two postulates
One postulate
None of these
Previous
Skip
Next
Question # 12
When monochromatic light is allowed to fall on cathode, it begins to emit electrons, these electrons are called
Choose an answer
thermoionic electrons
free electrons
photoelectrons
slow electrons
Previous
Skip
Next
Question # 13
Compton shift refers to:
Choose an answer
Photon
Meson
Proton
Positron
Both (B) and (D)
Previous
Skip
Next
Question # 14
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
Previous
Skip
Next
Question # 15
The value of threshold frequency for different metals is
Choose an answer
different
same
may be different or may be same
none of these
Previous
Skip
Next
Question # 16
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
Previous
Skip
Next
Question # 17
The stopping voltage for a certain metal is 100 volts, then the work function for the cathode plate is
Choose an answer
100 J
1.6 x 10
-17
J
100 eV
1.6 x 10
-17
eV
Previous
Skip
Next
Question # 18
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
Previous
Skip
Next
Question # 19
Max plank founded a mathematical model resulting in an equation that describes the shape of observed black body radiation curves exactly, in
Choose an answer
1890
1895
1900
1905
Previous
Skip
Next
Question # 20
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)
Previous
Skip
Next
Question # 21
When a platinum wire is heated, it appears orange red at
Choose an answer
500
°C
900
°C
1100
°C
1300
°C
Previous
Skip
Next
Question # 22
Electromagnetic -radiation means:
Choose an answer
Photons
protons
Electrons
Mesons
None of these
Previous
Skip
Next
Question # 23
In photoelectric effect the energy of ejected electrons depend on
Choose an answer
The frequency
The intensity
Both frequency and intensity
None of these
Previous
Skip
Next
Question # 24
The positron was discovered by:
Choose an answer
In cosmic radiation
In 1932
By Carl Anderson
All above
By direc
Previous
Skip
Next
Question # 25
If a material object moves with the speed of light 'C' its mass becomes
Choose an answer
Equal to its rest mass
Four times of its rest mass
Double of its rest mass
Infinite
Previous
Skip
Next
Question # 26
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
Previous
Skip
Next
Question # 27
From the theory of relativity, momentum p of the photon is related to energy as
Choose an answer
p = hfc
p = hf/c
p = f(hc,f)
p = cf/h
Previous
Skip
Next
Question # 28
According to the special theory of relativity
Choose an answer
mass and energy are same entities
mass and energy are same entities but interconverible
mass and energy are different entities but interconverible
mass and energy are different entities but non-interconveritble
Previous
Skip
Next
Question # 29
The existence of position was predicted by Dirace in
Choose an answer
1920
1925
1930
1928
Previous
Skip
Next
Question # 30
The ratio of energy E to the corresponding frequency (f) of the radiation (emitted or absorbed) is called:
Choose an answer
Wien's constant
Stefen's constnat
Planck's constant
Boltzmann's constant
None of these
Previous
Skip
Next
Question # 31
Converse of pair production is known as
Choose an answer
Compton effect
annihilation of matter
photoelectric effect
none of these
Previous
Skip
Next
Back