Show all the work please! For each statement, decide whether it is always true,
ID: 1310988 • Letter: S
Question
Show all the work please!
For each statement, decide whether it is always true, always false or true in certain circumstances. State which case applies to the statement, describing why you chose the answer you did and cite an experiment or principle of Physics which supports your claim. [1] Electromagnetic waves are composed of moving electric charge with no mass. [2] The intensity of light from a source decreases linearly with hte distance from the Source. [3] An electron and a positron having equal and opposite angular momentum annihilate producing two photons. The polarizations of the two photons are the same. [4] When laser light reflects off a very low mass mirror hung from its center in a vacuum. the mirror rotates away from the laser beam while a similar situation with a black absorptive surface in place of the mirror will rotate in the opposite direction. [5]Light has no mass and, therefore, no momentum. [6] Light from a laser shines through a pair of closely spaced slits, after which it strikes a screen, forming a pattern of bright and dark stripes or fringes. If the slits are spaced farther apart, the spacing between fringes increases. [7] Now, if the width of the slits is decreased. the width of the central region also decreases but the fringe spacing stays the same. [8] As light is reflected from a thin film. a beam results. the same as if it reflected from a mirror. [9]If light passes through a single narrow slit, the pattern on a screen beyond is a single spot with fuzz edges. [10] A laser beam passes through two polarizers next to each other. one vertical. the other horizontal. Behind each polarizer is a narrow slit with a small space between them. The pattern seen on the screen beyond is the same as that for a double slit without the polarizers.Explanation / Answer
i dont know answers to two or three qs given but i have answer to rest qs
1.)Electromagnetic waves are composed of moving electric charge with no mass:-
Always true, An electromagnetic wave can be created by accelerating charges; moving charges back and forth will produce oscillating electric and magnetic fields, and these travel at the speed of light. It would really be more accurate to call the speed "the speed of an electromagnetic wave", because light is just one example of an electromagnetic wave.
The two points are key to understanding electromagnetic waves.
An electromagnetic wave (such as a radio wave) propagates outwards from the source (an antenna, perhaps) at the speed of light. What this means in practice is that the source has created oscillating electric and magnetic fields, perpendicular to each other, that travel away from the source. The E and B fields, along with being perpendicular to each other, are perpendicular to the direction the wave travels, meaning that an electromagnetic wave is a transverse wave. The energy of the wave is stored in the electric and magnetic fields. An electromagnetic wave, although it carries no mass, does carry energy. It also has momentum, and can exert pressure (known as radiation pressure). The reason tails of comets point away from the Sun is the radiation pressure exerted on the tail by the light (and other forms of radiation) from the Sun.
2.) The intensity of light from a source decreases linearly with the distance from the source:-
always false, because it follows inverse square law
The inverse-square law for light intensity states: The intensity of illumination is proportional to the inverse square of the distance from the light source.
3.) An electron and a positron having equal and opposite angular mommentum annhilates producinhg two photons. The polarization of the two photons are same:-
True under certain condition, When an electron and positron combine the initial product is positronium but, after a short time, high-energy photons are produced and all trace of the original two particles is lost. Since the amount of energy carried away by the photons is exactly equal to the rest-mass equivalent of positronium (1.022 MeV), it is natural to interpret this process as involving the complete destruction of the original two particles. In general, the more exothermic such a process, the more intuitively reasonable such an explanation becomes. Yet it cannot be proven with certainty that the electron and positron pass out of existence, because it is impossible to eliminate the possibility that a new state has been reached which cannot be detected by experimental means. Under the circumstance, one is justified to make the opposite assumption and see if it leads to any sort of contradictory result.
In the present case, this procedure forces one to assume that even in positronium decay there is elemental balance, in particular that the electron and positron at the start of the reaction are still present in a real form at its conclusion as well. Consistency with the arguments given in the Introduction requires one to assume that the photons produced at the end of the decay process were present in a massless and therefore undetectable form at its beginning, so there is no new difficulty provided by this aspect of the experimental observations. The situation with the electron and positron is less clear, however, because they have a combined rest mass equivalent to 1.022 MeV and are already in their lowest translational state at the beginning of the process.
4.) when a laser light reflects off a very low mass mirror hung from its centre in vacuum, the mirror rotates away from the laser beam while a similar situation with a black, absorptive surface in place of a mirror will rotate in opposite direction:-
5.) light has no mass therefore no momentum:-
Always false, light has no mass but has momentum because at high speeds the formula p = m*v is not valid any longer;
for massive particles the formula becomes:
p = m*v*? where ? = 1/sqrt[1 - (v/c)2] v is the particle' speed.
for particles in general (massive or massless as photons):
p = sqrt[(E/c)2 - (mc)2] where E = total energy of the particle.
Look at the last formula: if m = 0, p = E/c. So, massless particles (as photons) have momentum if they have energy.
6.) Light from a laser shines through a pair of closley spaced slits, after which it strikes a screen, forming a pattern of bright and dark stipes or frindges.If the slits are spaced father apart, the spacing between the frindges increases:-
8.) As light is reflected from a thin film,a beam results,the same as if it is reflected from a mirror:-
True always,
9.) If light passes through a single narrow slit, the pattern on a screen beyond is single spot with fuzz edges:-
True always, the central maximum is larger than those on either side, and that the intensity decreases rapidly on either side. In contrast, a diffraction grating produces evenly spaced lines that dim slowly on either side of center.