What is the definition of diffusion?

Diffusion is the random motion of molecules from an area of higher concentration to an area of lower concentration.

Molecules tend to move constantly in solution and spread out randomly. When the concentration of particles in solution is spread evenly throughout, the solution is at an equilibrium. 

In a cell, the membrane creates a selectively permeable barrier between the interior of the cell and the exterior surroundings. If there is a difference in concentration of a solute on one side of the membrane, diffusion will occur from high to low concentration until equilibrium is achieved. This explains how oxygen (in higher concentration outside the cell) enters the cell by diffusion through its membrane.

It is important to note that the cell doesn't expend any additional energy for diffusion to occur. It is an example of passive transport.

I have included a link which has an excellent diagram showing diffusion.

While it is a common assumption that Moses wrote the Torah, most scholars argue that the Torah was compiled from different documentary sources many...

According to the Documentary Hypothesis, also called the Wellhausen Hypothesis, the Torah (the first five books of the Bible) were drawn from four separate narratives and were later combined into a whole by redactors, or editors. The evidence for this hypothesis comes from the literary analysis of the Torah, including an analysis of the different names used in the Torah for God ("YHWH" or "Yahweh" or "Elohim") and repeated stories, or "doublets." Many scholars have come to believe that there were four sources of the Torah--"J" or the "Yahwist" source; "E" or the "Elohist" source; "D" or the Deuteronomist; and "P," or the Priestly source. These sources are thought to have written in order, from "J" to "P," in the period c. 950 BCE to c. 500 BCE. Each source is thought to have a different style. One of the doublets in Genesis is the creation story in Genesis 1 and the repeated story of creation along different lines in Genesis 2. In Genesis 1, the story of creation is described in seven days, but in Genesis 2, the story of creation is described with Adam and Eve's fall from grace in the Garden of Eden. In addition, the narrative of the flood, in Genesis 6-9, is given in different and at times contradictory accounts and described in repetitive ways.

Genesis 1-11, therefore, cannot be read as a coherent narrative, as it has many contradictions and duplications. The benefit of literary analysis applied to the Torah is that it allows scholars to understand the history of Judaism, including its changing nature. For example, many scholars have hypothesized that there was a growth in priestly power over the course of time, as "P" is thought to be the last source. However, many religious figures and institutions continue to believe in Mosaic authorship of the Torah--that is, that Moses wrote the Torah when he received it by God. Believing otherwise is contrary to Orthodox Jewish faith and to the beliefs of some Christian churches. 

Can you help me paraphrase "She Dwelt Among the Untrodden Ways" by William Wordsworth?

Despite its compact form, William Wordsworth's "She Dwelt Among the Untrodden Ways" is a dense poem that incorporates many layers of meaning. As such, it can be quite difficult to paraphrase, especially if you're feeling unsure about the meaning of the poem. Though there's a great deal going on here, for our purposes I think it would be fine to focus on one aspect of the poem: the recognition of the ways in which the most ordinary being can still be existentially significant.

With this idea in mind, here's an example of a very short paraphrase of this poem:

Lucy, a young, relatively unknown girl, lived alone in nature far from conventional human society. Her dwelling place abounded with a great deal of natural beauty. Since she lived alone and had few connections to society, her death went more or less unnoticed. Even so, Lucy's death is considered to be highly significant for the narrator and (it's implied) an immense source of grief.

This quick paraphrase hardly does Wordsworth's excellent verse justice; however, it does highlight an important theme in the poem: the idea that even the most common person can achieve great significance. With this idea in mind, read the poem again and try to come up with your own paraphrased version.

How do you calculate the surface area of a rectangular prism?

You would add area of all the sides up.  Now, that's literally the formula I like to consider.  And, that will work for any non-circular prism, period.  

Now, special formulas do exist for specific types of prisms, for instance, a rectangular prism, you could consider the formula for the area of one side, length x width, then consider there is another one of those sides, so two of them, so 2 x length x width.  Then, pick another side and find that area, like width x height.  And, there is another one of those, so 2 x width x height.  And, likewise for length x height.  There would be 2 x length x height.  So, adding those up, you would have:

total area rectangular prism = 2LW + 2LH + 2WH

where L = length, W = width, and H = height

How is Eric Birling presented in An Inspector Calls?

Eric Birling is first presented as the ne'er-do-well son of the wealthy and hardheaded businessman Arthur Birling, but later he proves his worth as an honest man.

Eric is an alcoholic, whose behavior has been dissolute and irresponsible, but his mother pretends that there is nothing wrong with her son. In the end, unlike his parents, Eric, along with his sister, demonstrates that he does possess a moral compass and a worthy conscience, by not excusing his guilt in the death of a poor young woman.

While the Birling family enjoys a celebratory dinner for their daughter Sheila and her fiance Gerald Croft, a police inspector arrives to question the family about a young woman named Eva Smith, who later calls herself Daisy Renton, who has committed suicide. The inspector shows each person separately a photograph, and he describes the poor girl's history.

At first, he talks to Mr. Birling and Gerald. However, as the drama develops, it is demonstrated all of the Birlings are involved in the tragic events that lead poor Eva to taking her life. The inspector also reveals that both Gerald and Eric have been romantically involved with Eva after her firing at the Birling factory and another job.

When Eva, who calls herself Mrs. Birling, appears before Mrs. Sybil Birling's charity group to appeal for financial help, the outraged Mrs. Birling prevents Eva from obtaining anything. She insists, ironically, that the father of the child must be held responsible. Eva tells her that this young man has given her some money, but she suspects that it has been stolen, so she cannot accept anything from him. (The young man, of course, is Eric and his impregnating Eva is why she has called herself Mrs. Birling.)

After all the inspector's revelations, Eric and his sister Sheila, who caused Eva's firing from a dress shop, admit their guilt. Further, Eric confesses to his father that he did, in fact, steal fifty dollars which he gave to Eva. Arthur Birling's first reaction is how to cover up the loss of the fifty dollars so no one will know. He tells his children that "a man has to mind his own business and look after himself and his own."

Further, Birling says there is reason to excuse his and his wife's behavior, but he is ashamed of Eric. On the other hand, Eric replies that he is ashamed of them, as well, as his father began her misfortunes and his mother directly caused her and his child to die. Nevertheless, in the end, the parents justify their actions because the inspector has performed a ruse and is not a real policeman. Only Eric and his sister accept their social responsibilities.

Under what conditions does a convex mirror form a real image?

A convex mirror is made by applying a reflective coating on the outside of a piece of a curved surface. The center of curvature of and the focal point of the mirror are thus on one side of the mirror, but the object is on the other side. (Please see the attached reference link for the illustration.) 

When the light rays hit the mirror, they are reflected back in a way that that the angle of reflection (the angle the reflected ray makes with the normal to the surface) is equal to the angle of incidence (the angle the incident ray makes with the normal.) Because the mirror is convex, the reflected rays point away from the focal point of the mirror, or diverge. Therefore, the rays do not intersect, but their extensions do intersect, forming a virtual image. This is true no matter how far away the object is located from the mirror. Again, please see the reference link for the diagram of the image formation by a convex mirror.

As discussed above and can be seen from the diagram, it is impossible to obtain a real image in a convex mirror. The convex mirrors always form virtual images.

In "The Dead" by James Joyce, what is the significance of Gabriel seeing himself in the mirror?

Here are the passages that describe the moment that Gabriel sees himself in the mirror (they don't have page numbers because they're taken from ' excellent online version of the text): 

As he passed in the way of the cheval-glass [Gabriel] caught sight of himself in full length, his broad, well-filled shirt-front, the face whose expression always puzzled him when he saw it in a mirror, and his glimmering gilt-rimmed eyeglasses. 

Later, Gabriel muses on this experience in a fairly negative way: 

[Gabriel] saw himself as a ludicrous figure, acting as a pennyboy for his aunts, a nervous, well-meaning sentimentalist, orating to vulgarians and idealising his own clownish lusts, the pitiable fatuous fellow he had caught a glimpse of in the mirror. 

All of this happens around the time Gretta, Gabriel's wife, tells him about Michael Furey, the young man she loved in her youth in Galway. The story is a romantic one, and Gabriel quickly realizes that he is not his wife's true love after all and that he has never captured her affection the same way this young man did. Within this context, Gabriel's bitter evaluation of his reflection becomes very important. Gabriel's reflection in the mirror becomes a physical manifestation of his realization that he is not as important as he seems. Indeed, the reflection underlines Gabriel's sudden recognition of his own ridiculousness and relative insignificance. In that case, Gabriel's sight of himself in the mirror becomes a pivotal turning point in the text, as it is the beginning of the epiphany that ultimately destroys Gabriel's illusions about himself and forces him to reassess some of the most significant aspects of his life.