Download Ch # 17 Advent of Modern Physics Special Theory Of Relativity

Ch # 17
Advent of Modern Physics
Special Theory Of Relativity
Question and Answers
1. What do you understand by the Frame of Reference and inertial Frame of Reference? Give
one example of each.
2. What are the postulates of special theory of relativity? Explain the results of Einstein's
special theory of relativity.
3. How does Lorentz transformation help in any way explaining the Special theory of Relativity?
4. What is Relative energy?
5. What is Length contraction?
6. What is Relative Mass?
7. What is Time Dilation?
State postulates and discuss results of special theory of relativity.
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Numerical
1) Find the mass of an object moving with speed 0.8C.
2) At what speed must a particle move for m to be 2mo
3) A what speed the rest energy of an object of mass mo is equal to its kinetic energy
4) Compute the rest energy of
(1) An electron
(2) Proton
(3) Alpha Particle
5) Determine the apparent mass and speed of an electron having kinetic energy 105eV.
6) Compute the apparent mass of an electron traveling at half the speed of light.
7) How fast must an object be moving if its apparent mass is to be 1 percent larger than its
rest mass.
8) An electron's relativistic mass is found to be 75% more than its rest mass (i.e. m =
1.75m0). Calculate its (i) velocity (ii) kinetic energy in eV & (iii) total energy in eV.
MCQs
1. Modern physics consists of __________. (Newtonian Mechanics, Einstein’s special
theory of relativity, Schrodinger’s wave mechanics, Einstein’s special theory of
relativity and Quantum mechanics)
2. The most fundamental to classical physics is/are __________. (Maxwell’s equations,
Schrodinger’s wave equation, Law of newtonian mechanics, Special theory of
relativity)
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3. __________ believed in absolute time. (Einstein, Maxwell, Galileo, Galileo and
Newton)
4. A set of coordinate axes with respect to which measurements are made is called
__________.
5. (frame of reference, inertial frame of reference, non-inertial frame of reference, none
of these)
6. Every motion is __________. (relative, absolute, zero, none of these)
7. A frame of reference in which Newton’s laws of motion are valid is called
__________.
8. (Cartesian frame of reference, inertial frame of reference, non-inertial frames of
reference, absolute frame of reference)
9. A frame of reference in which Newton’s laws of motion are not valid is called
__________.
10. (Cartesian frame of reference, inertial frame of reference, non-inertial frames of
reference, absolute frame of reference)
11. __________ of the Newtonian laws don not hold in an accelerated frame of
reference.
12. (Newton’s first and second law of motion, Newton’s scond and third law of motion,
third law of motion, Newton’s first law of motion and law of Gravitation)
13. __________ of the following statements is not correct. (the law of physics are the
same in all inertial frames, the speed of light in free space has the same value in all
inertial frames, two events which occur simultaneously in one reference frame also
must appear to occur simultaneous in another reference frame, Einstein rejected
Newton’s idea of absolute time)
14. Special theory of relativity states that __________. (All laws of physics are the same
in every inertial reference frame, Every motion is relative, Light has dual nature,
Energy and mas are interconvertable)
15. Special theory of relativity states that __________. (Time is absolute, The speed of
light in a vacuumm, measured in all inertial reference frames always has the same
value of c, no matter how fast the source of light and the observer are moving relative
to each other, space is absolute, at rest mas of an object is always zero)
16. The simple assumption that all possible reference frames moving with uniform
velocity relative to one another are equivalent for the statement of laws of physics is
called the __________. (Principle of Relativity, Uncertainity Principle, Pauli’s
Exclusion Principle, None of these)
Black Body
Question and Answers
17. What is Black Body? What is Black Body radiation?
18. State the laws governing the black body radiation. Write mathematical expression.
Numerical
1. What will be the wave length of radiation associated with temperature of 37 0C (constant =
0.0029mk)
2. At what temperature a block body emits a wave length of 7.8 –m
MCQs
1. A body of some material capable of absorbing all heat radiation incident on it and
can emit in turn all the radiation at constant temperature after it is in equilibrium
with it is called __________. (Black body, Black body radiation, Black body
cavity, Cavity radiation)
2. Rayleigh Jeans theory is incomplete disagreement with the experimental curve of
black body radiation __________.
3. (In the region of short wavelength, in the region of long wavelength, both in the
region of short and long wavelength, none of these)
4. Wein’s theory is complete disagreement with the experimental curve of black
body radiation __________.
5. (In the region of short wavelength, in the region of long wavelength, both in the
region of short and long wavelength, none of these)
6. In 1900, __________ proposed a formula which explained I detail the whole
shape of the black body spectrum for all wavelengths. (Wein, Rayleigh, Einstein,
Maxwell Plank)
7. __________ proposed quantum theory of radiation. (Wein, Einstein, Plank,
Newton)
8. __________ theory explains that energy exchange takes place in discrete
“bundles” or “quanta”.
9. (Special theory of Relativity, Quantum Theory, Corpuscular Theory, Bohr’s
Theory)
10. Mathematically Quantum theory is states as __________. (E = mc2, E = hf, v =
nl, none of these)
11. Light consists of particle wave called __________. (Proton, Electron, Neutron,
Photon)
Quantum Physics
Question and Answers
1. What is Stefan’s Law, Reylaigh Jeans’s law, Planks law?
2. Describe Compton’s effect? Derive the formula for the Compton’s shift.
3. State and prove De-Broglie’s idea.
4. Define Pair Production and Annihilation.
5. State and Explain Uncertainty principle.
Numerical
1. Find the energy photon in
(a) radio wave of wave length 100nm
(b) Green length of 550 nm
(c) X-rays of wave length 0.2 nm
2. What is the wave length and frequency of photon associated with 1.0 eV energy.
Yellow light of wave. Length 577 nm is incident on a cesium surface. The stopping voltage is
found to be 0.25V.
Find (a) the maximum K.E of photoelectrons
(b) the work function of cesium
3. The work function of sodium metal is 2.3 eV what is the longest wavelength that can cause
photo electron emission from sodium?
4. What P.d must be applied to stop the fastest photo electrons emitted by a nickel surface under
the action of U.V light of wavelength 200nm? The work function of nickel is 5.01V
MCQs
1. The rest mass of photon is __________. (One, Zero, Infinite, None of these)
2. In 1905, __________ proposed that the packets or bundles of energy are integral
part of all electromagnetic radiations. (Plank, Einstein, Newton, Wein)
3. The process of ejection of loosely bound electrons from a metallic surface by the
absorption of photons is called _________. (Pair production, Compton Effect,
Photoelectric effect, Uncertainity Principle)
4. In Compton Effect __________. (The scattered photon has frequency less than
that of the incident photon, the scattered photon has frequency greater than that
of the incident photon, the scattered photon has frequency equal to the incident
photon, none of these)
5. On moving from one place to another electromagnetic radiation behaves as
_________. (particles, waves, both particles and waves, none of these)
6. Electromagnetic radiation when interact with material particle, behaves as
__________. (particles, waves, both particles and waves, none of these)
7. When we try to stop a very high photon it loses its identify and disintegration into
an electron and a positron. This is called __________. (Pair production,
Annihilation, X-rays production, Compton effect)
8. A process reverse to the pair production is known as __________. (Photoelectric
effect, Annihilation, X-rays production, Compton Effect)
9. When an electron and a positron combine together in such a way that both of
them disappear and their combined mass reappear as two gamma ray photons.
This is called __________. (Photoelectric effect, Annihilation, X-rays production,
Compton effect)
10. “The product of the uncertainties in momentum (Dp) and position)Dx) of particle
at some instant is approximately fo the order of Plank’s constant h”. This is called
__________.
11. (Pauli’s Exclusion Principle, Heisenberg Uncertainity Principle, Photoelectric
effect, Compton effect)
Photo electric effect
Question and Answers
1.
2.
3.
4.
5.
What is Photoelectric effect? What remarkable results were obtained?
Give Einstein’s explanation of the photoelectric effect.
Derive equation of Photo electric effect.
What are Threshold frequency, Work function, and stopping potential?
What is a Photo cell? Give its uses in daily life.
6. Describe results of photoelectric effect as explained by Einstein.
7.
The work function of a metal is 4eV. Will it emit photons if illuminated with a light of
wavelength 30000Å? Give reason for your answer.
MCQs
1. The photoelectric effect establishes that __________. (Light travels in the form of
inertial of quanta of energy, Light travels in the form of transverse waves, light
travels in the form of longitudinal waves, light is a transverse electromagnetic
wave)
2. The photoelectric emission from the surface of a metal starts only when the light
incident on the surface has a certain __________. (minimum frequency,
minimum wavelength, minimum intensity, minimum speed)
3. At frequencies of the incident radiation above the threshold frequency, the
photoelectric current in a photoelectric cell increases with the increase in
__________. (intensity of incident radiation, wavelength of incident radiation,
frequency of incident radiation, speed of incident emitted from a metal surface)
4. The photoelectrons emitted from a metal surface __________. (are all at rest,
have the same kinetic energy, have the same momentum, have speeds varying
from zero up to a certain maximum value)
5. For each material emission occurs only for certain definite frequency fo of light
called __________.
6. (1 Hertz, Critical frequency, threshold frequency, minimum frequency)
7. Amount of energy in a photon depends on the __________. (rest mass,
frequency, momentum, wavelength)
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8. The minimum energy of an electron that must have in order to escape from the
metal surface is called __________.
9. (Stopping potential, work function, threshold frequency, wavelength)
10. Photoelectric effect is a phenomenon in which electromagnetic waves exhibit
__________.
11. (Wave nature, particle nature, both wave and particle nature, none of these)