1
Q
Who discovered X-rays?
A
W C Roentgen
2
Q
Who discovered the electron?
A
J J Thomson
3
Q
Which experiment measured electron charge?
A
Millikan oil-drop experiment
4
Q
What does quantisation of charge mean?
A
Charge exists in integral multiples of elementary charge
5
Q
What does work function depend on?
A
Nature of metal and surface condition
6
Q
Who discovered photoelectric effect?
A
Heinrich Hertz
7
Q
What happens below threshold frequency?
A
No photoelectric emission occurs
8
Q
Which metals need UV light?
A
Zinc cadmium magnesium
9
Q
Which metals respond to visible light?
A
Alkali metals like Na K Cs
10
Q
How does photoelectric current depend on intensity?
A
Directly proportional
11
Q
What is saturation current?
A
Maximum value of photoelectric current
12
Q
What happens when collector polarity is reversed?
A
Only high energy electrons reach collector
13
Q
What is stopping potential?
A
Minimum negative potential to stop photocurrent
14
Q
What does stopping potential represent?
A
Maximum kinetic energy of photoelectrons
15
Q
How does kinetic energy depend on intensity?
A
It is independent of intensity
16
Q
How does kinetic energy depend on frequency?
A
It increases linearly with frequency
17
Q
What happens at frequency below cut-off?
A
No photoelectric emission
18
Q
Does photoelectric emission have time lag?
A
No emission is instantaneous
19
Q
What is time scale of emission?
A
About 10^-9 s or less
20
Q
Can wave theory explain photoelectric effect?
A
No wave theory fails
21
Q
How is radiation energy distributed?
A
In discrete packets called quanta
22
Q
What does intensity control in photoelectric effect?
A
Number of emitted electrons
23
Q
What does frequency control in photoelectric effect?
A
Energy of emitted electrons
24
Q
Who verified photoelectric equation?
A
Millikan
25
Are photons electrically charged?
Photons are electrically neutral
26
Are photons deflected by electric fields?
No photons are not deflected
27
Are photons deflected by magnetic fields?
No photons are not deflected
28
What is conserved in photon-particle collision?
Total energy and total momentum
29
Is number of photons conserved in collisions?
No number of photons is not conserved
30
What can happen to a photon in collision?
Photon may be absorbed or created
31
Which phenomena show wave nature of light?
Interference diffraction and polarisation
Wave nature: Interference, diffraction, polarization
Particle nature: Photoelectric effect, Compton effect
32
Which effects show particle nature of light?
Photoelectric effect and Compton effect
33
How does radiation behave in photoelectric effect?
As particles called photons
34
What does energy transfer indicate?
Particle nature of radiation
35
What does momentum transfer indicate?
Particle nature of radiation
36
Who proposed matter waves?
De Broglie
37
intensity directly proportional to
no. of photon l no of electrons emitted l photocurrent
38
frequency directly proportional to
energy of photon l energy of electrons emitted l stopping pot
39
What was the first model of the atom?
Plum pudding model proposed by J J Thomson describing atom as positive charge with embedded electrons
40
What spectrum is associated with each element?
Each element has a characteristic spectrum of radiation
41
What is Rutherford nuclear or planetary model?
Entire positive charge and most mass concentrated in a small nucleus with electrons revolving around it
42
What was a limitation of Rutherford model?
It could not explain why atoms emit light of discrete wavelengths
43
What observation shows atom is mostly empty?
Most alpha particles passed through foil without collision
44
What fraction of alpha particles were strongly deflected?
Only a very small fraction were deflected through large angles
45
What does large angle deflection indicate?
Presence of a small dense positively charged nucleus
46
What are main features of Rutherford nuclear model?
Positive charge and mass in nucleus with electrons at some distance revolving in orbits
47
How do electrons move in Rutherford model?
Electrons revolve around nucleus like planets around the sun
48
What does comparison of sizes imply?
Most of the atom is empty space
49
What does negative total energy of electron indicate?
Electron is bound to the nucleus
50
What is an emission line spectrum?
Spectrum with only specific wavelengths emitted by excited atomic gas
51
How is emission line spectrum produced?
By exciting gas or vapour at low pressure using electric discharge
52
What is absorption spectrum?
Spectrum with dark lines when white light passes through a gas
53
Why do dark lines appear in absorption spectrum?
Gas absorbs the same wavelengths it can emit
54
According to classical electromagnetic theory frequency of emitted radiation equals what?
Frequency of revolution of the electron
55
What was Bohr first postulate?
Electron revolves in certain stable orbits without emitting energy
56
What does Bohr second postulate state?
Electron revolves only in orbits with quantised angular momentum
57
According to Bohr second postulate angular momentum equals what?
Integral multiple of h divided by two pi
58
What does Bohr second postulate imply about angular momentum?
Angular momentum of electron is quantised
59
What does Bohr third postulate state?
Energy difference between two states is emitted as a photon
60
When is a photon emitted according to Bohr model?
When electron jumps from higher to lower energy state
61
What carries energy during electronic transition?
Photon of specific frequency
62
What is the process called when atom absorbs photon?
Absorption
63
What happens when continuous radiation passes through rarefied gas?
Dark absorption lines appear in spectrum
64
What do absorption lines indicate?
Frequencies absorbed by atoms of the gas
65
What are isotopes of hydrogen?
Protium deuterium and tritium
66
Why is tritium absent in nature?
It is unstable and produced artificially
67
What is mass ratio of hydrogen isotopes?
One two three
68
What does isotope mass ratio indicate?
Presence of neutral matter in nucleus
69
Who confirmed neutral matter?
James Chadwick
70
What are neutral nuclear particles?
Neutrons
71
Is free neutron stable?
No it decays
72
How does free neutron decay?
Into proton electron and antineutrino
73
How does nuclear radius depend on mass number?
Radius proportional to cube root of mass number
74
What does radius relation imply?
Volume proportional to mass number and constant density
75
Order of density of nuclear matter ?
About 10^17
76
What did Einstein show about mass?
Mass is a form of energy
77
What does mass energy equivalence mean?
Mass converts to energy and vice versa
78
How does binding energy per nucleon vary?
Nearly constant for middle mass nuclei
79
For which mass range is binding energy constant?
Mass number thirty to one hundred seventy
80
Where is binding energy per nucleon maximum?
Iron with mass number fifty six
81
What is average binding energy per nucleon?
About eight mega electron volt
82
Why is binding energy nearly constant?
Due to short range nuclear force
83
How strong is nuclear force?
Much stronger than Coulomb and gravitational forces
84
Why must nuclear force dominate?
To overcome proton repulsion in nucleus
85
How does nuclear force vary with distance?
Falls rapidly beyond few femtometres
86
At what distance is nuclear force minimum?
About zero point eight femtometre
87
Nature of force below zero point eight femtometre?
Repulsive
88
Nature of force above zero point eight femtometre?
Attractive
89
Does nuclear force depend on charge?
No it is same for all nucleon pairs
90
Is there a simple law for nuclear force?
No simple mathematical law
91
What are types of radioactive decay?
Alpha beta and gamma
92
What is emitted in alpha decay?
Helium nucleus
93
What is emitted in beta decay?
Electron or positron
94
What is emitted in gamma decay?
High energy photons
95
How does fission energy appear initially?
As kinetic energy of fragments and neutrons
96
How does fission energy become usable?
Converted into heat
97
What powers nuclear reactors?
Nuclear fission
98
What is thermonuclear fusion?
Fusion due to very high temperature
99
What powers stars like the sun?
Thermonuclear fusion
100
What is fuel of the sun?
Hydrogen converting to helium
101
What happens when hydrogen ends in star core?
Core collapses increasing temperature
102
103
Up to which elements can fusion occur?
Up to elements near iron
104
Why cannot heavier elements form by fusion?
Binding energy decreases beyond iron
105
Is nuclear force same for all nucleons?
Yes it is approximately the same
106
Does nuclear force depend on charge?
No it is charge independent
107
What is charge independence of nuclear force?
Same force for nn pp and np
108
Bohr’s atomic model – NCERT one-line summary of postulates:
Electrons revolve around the nucleus only in certain permitted circular orbits called stationary states without radiating energy.
Each orbit has a fixed energy, and energy remains constant as long as the electron stays in that orbit.
Energy is emitted or absorbed only when an electron jumps from one orbit to another, with ΔE = hν.
Only those orbits are allowed for which the angular momentum of the electron is quantized:
mvr = n h / 2π (n = 1, 2, 3 …)
Erwin Smith
flashcards
Decks in class (16)
# Cards
-
Qualitative Quantitative Analysis Kjhedahl26
-
OC Tests57
-
Titration, Indicator, Redox52
-
Salt Analysis107
-
Purification69
-
Modern Physics Final108
-
Thermodynamics Final56
-
Semiconductor Flashcards44
-
Battery And Corrosion62
-
P Block 1291
-
P Block 11169
-
DF block166
-
Name Reactions54
-
Heat New57
-
Biomolecules 🧬63
-
Name1
