3

## The radius of the sun is 0.7 million km. What percentage of the radius is taken up by the chromosphere?

Hunaid L. Hanfee
Featured 10 months ago · Astrophysics

0.28%

#### Explanation:

The layer chromosphere is $2000$ km thick.

The radius of the sun is $0.7 \cdot {10}^{6}$ km.

To calculate this you have to just do same as we do in calculation of our exam's marks percentage.

Just imagine,

Your exam is of total marks of $0.7 \cdot {10}^{6}$(not possible but you have $\textcolor{w h i t e}{0000000000000000000000000000000}$to just imagine this )
out of this you got $2000$ marks.

To calculate the percentage you have to do something like this:

$= \frac{2000}{0.7 \cdot {10}^{6}} \cdot 100$

Right?

Just do same calculation for this question,
Total radius of sun is $0.7 \cdot {10}^{6}$ km.
out of this $2000$ km is chromosphere.

$= \frac{2000}{0.7 \cdot {10}^{6}} \cdot 100$

$= 0.002857 \cdot 100$

=0.28%

I have added image for your help by which you can know where is chromosphere of the sun.

# Make the internet a better place to learn

65

## How did Socratic start?

Christopher P.
Featured 20 hours ago · Socratic Meta

I first met Shreyans Bhansali in early 2013. We had both spent years working at tech companies (Google, Venmo) and wanted to work in education.

We saw education as the "root of all good": we thought we could either try to tackle every problem in society one by one, or we could try to give more people access to better education so they'd be empowered to tackle more problems.

We looked at the internet and saw this amazing communication medium which was falling short of its promise of helping students.

When students turned to the internet for help, they usually ended up on unhelpful sites like Yahoo Answers or Wiki Answers.

We thought the internet could do a lot better. We'd seen online communities build amazing resources like Wikipedia and StackOverflow when they were driven by a shared mission and we knew there were a lot of people in the world who cared about students having free access to better learning content.

So we started building Socratic.

The first version of Socratic was extremely simple and Chemistry was the only subject available. Tyler DeWitt became the first teacher to add content. Soon after, David joined as our designer and Kuba joined as engineer.

The Socratic community started growing and soon included people from all over the world contributing to making learning easier.

20

## Why should we think twice before answering questions with phrases such as, "it's really simple" or "the solution is very easy"?

Kate M.
Featured 20 hours ago · Socratic Meta

Because what seems easy, straight-forward, or simple to you may be something a student has struggled to understand for a while now.

#### Explanation:

One of the best parts about Socratic is that it is an anonymous way for students to ask questions, even very basic questions. When we answer a question with, "If you think about it, it's really simple" or something along these lines, you might not realize that a topic you find easy to understand is a topic the student has seriously struggled with.

These phrases seem harmless, and some of the time they probably are. Other times a student may have already asked a teacher for help, searched for the answer on the internet, and that student is still stuck. Many students of all ages don't feel comfortable enough to raise their hand in class and ask for help, but they should be able to do so here. By saying, "If you think about it, it's really simple," you imply that the person hasn't thought about the topic, and you imply that the answer is easy, which it might not be.

Everyone has struggled with some subject at one point in their life, and for all you know, the person asking this question might be having a very difficult time, so, in my opinion, omit these types of phrases and stick to explaining the topic.

16

## How can I send someone a note or message on Socratic?

Becca M.
Featured 20 hours ago · Socratic Meta

There's been a new update to messaging on Socratic! Now you can privately message other community members and look back on your previous conversation.

#### Explanation:

If you'd like to send a personal message to someone else in the community, here's what you should do:

1. Find the person's profile by clicking their name anywhere it appears on the site (or, read how to search for people here)

2. Once on their profile, you'll see a blue "Send Message" button to the right of their name:

After clicking the button, you'll be taken to your conversation with that person ...

... and you are free to message them as you wish!

Happy messaging!

Other messaging resources:

6

Becca M.
Featured 20 hours ago · Socratic Meta

The Socratic community prides itself on writing answers to students' questions that actually teach the concepts.

On Socratic, the best answers leave students feeling empowered and inspired by understanding, rather than leaving them with just a quick answer.

Featured answers expose and celebrate such answers. They are examples of the very best we can create: answers that truly teach and make learning easier for students.

To see all the featured answers in a subject, click "view more" in the bottom right (shown with a green arrow above).

Featured answers are chosen by Socratic Heroes and subject moderators. To learn about the selection process, read this.

Having your answer chosen to be featured is something to be proud of and to strive for! But remember that not every answer can be featured, and learning how to write a featured answer is a skill you'll acquire with practice.

Let us know your questions and what you think of this feature in the comments!

13

## Is Socratic building an app?

Becca M.
Featured 20 hours ago · Socratic Meta

UPDATE

As of July 14, 2016, the Socratic app is available in the app store!

Original post:

Yes! As you know, we care deeply about helping students learn. When we started Socratic in 2013, we wanted to improve what students found when they turned to the Internet for help.

Three years later, this community has far exceeded that goal, and is still creating unbelievable answers every day. For that, students are emphatically grateful.

Every student deserves this experience. And today, when they're struggling, many students turn to their phones for help (some out of convenience; others because they simply don't have access to a desktop computer).

So we’re building an app that will bring the magic of the Socratic website directly to any student with a smartphone.

In the app, we hope to make the learning experience for students as accessible as possible.

We’ve built easier ways to ask a question, and we’ve used machine learning to analyze those questions and take students directly to the most relevant, helpful material—just as a tutor would.

In this way, the app will allow the learning content you create on the Socratic website to reach more students and help them in new ways, and we can’t wait to see just how far we can take this together. More students, more questions, more answers, more learning.

What do you think?

1

## What makes the rough endoplasmic reticulum rough?

Joëlle
Featured 6 hours ago · Biology

The ribosomes on the surface.

#### Explanation:

The rough endoplasmic reticulum (ER) is called 'rough' because it has organelles called ribosomes attached to the surface.

Ribosomes are the organelles that turn mRNA into proteins. These proteins are initially long strings of amino acids. This string has to be folded in the right way to form a functional protein. The rough ER helps with the folding of these amino acid-strings and at the same time prevents their degradation by enzymes in the cell.

Because of this cooperation, the ribosomes can be attached to the ER. The ribosomes can then synthesize the amino acid string straight into the ER, making the process safer and more efficient.

4

## How would you explain osmosis in terms of hypotonic, hypertonic and isotonic?

Featured 20 hours ago · Biology

Osmosis is the movement of water molecules from the region of their higher concentration to a region of lower concentration, across a semipermeable membrane.

#### Explanation:

Hypotonic solution have less solute (e.g NaCl) and more solvent (water) than your reference living cell.

(When a plant cell is put in a hypotonic solution, you will observe that plant cell become fully turgid due to endosmosis i.e water will enter into the cell.)

Hypertonic solution have more solute and less solvent compared to living cells.

(When a plant cell is placed in this solution, you will observe that the plant cell becomes flaccid due to exosmosis i.e. water will leave the cell. The plant cell is now called plasmolysed and the phenomenon is called plasmolysis.)

Isotonic solution have same amount of solute with respect to your selected cell.

(When you place a cell into the isotonic solution, there is no change in the structure of your cell as there is no net movement of water into or out of the cell, which means the number of water molecules that enter and exit the cell are same. )

2

## Rewrite in passive voice The students designed posters which they displayed in the public libary. Members of the schools Environmental Club undertook a beach clean up and collected over 15 sacks of garbage.? continue!

Fahmida
Featured an hour ago · English Grammar

Posters which they displayed in the public library, were designed by the students.

#### Explanation:

In the first sentence, "The students designed posters" is taken as its main clause, "which they displayed in the public library" is taken as subordinate clause and the voice change is done accordingly.

Take a look at the second sentence-

A beach cleanup was undertaken and over 15 sacks of garbage were collected by members of the school's Environmental Club.

I have changed both "bench cleanup" and "garbage" sections into passive form to make it meaningful.

1

## What is the orthocenter of a triangle with corners at (1, 6), (9, 1), and (5, 3)?

Dave G.
Featured 4 hours ago · Geometry

The point of intersection is $\left(- 22.5 , - 41\right)$

#### Explanation:

The orthocenter is where the altitudes intersect in a triangle. Technically, it's where all three altitudes meet. But we only need to find two of them - and it doesn't matter which two.

I've included two pictures - the first one is of the triangle (which is barely a triangle) and the other is a picture of the triangle, zoomed out, so we can see where the three altitudes intersect (so far outside the triangle!

So.... Let's find two of the altitudes. We'll need to know two things to find one altitude - one of the vertices, and the slope of the line that the altitude belongs to (we can just use the "rise over run" method for that.

Arbitrarily, let's start with the point $\left(5 , 3\right)$ and the line segment between $\left(1 , 6\right)$ and $\left(9 , 1\right)$. Some quick math, and the slope of that segment is $- \frac{5}{8}$ and the negative reciprocal is $\frac{8}{5}$. So let's use those two pieces of information to get the equation of that altitude!

$y - {y}_{1} = m \left(x - {x}_{1}\right)$

$y - 3 = \frac{8}{5} \left(x - 5\right)$

$y - 3 = \frac{8}{5} x - 8$

$y = \frac{8}{5} x - 5$

Sweet. Now let's do the same for a different altitude. Again, it doesn't matter which one. Let's pick the point $\left(9 , 1\right)$ and the segment with endpoints $\left(5 , 3\right)$ and $\left(1 , 6\right)$. Some counting gives us a slope of $- \frac{3}{4}$ so the slope of the altitude is $\frac{4}{3}$. Let's do this!

$y - {y}_{1} = m \left(x - {x}_{1}\right)$

$y - 1 = \frac{4}{3} \left(x - 9\right)$

$y - 1 = \frac{4}{3} x - 12$

$y = \frac{4}{3} x - 11$

Sweet.

Now we just need to find the point of intersection of those two altitudes. We can do that by setting them equal to each other.

$\frac{4}{3} x - 11 = \frac{8}{5} x - 5$

$\frac{20}{15} x - \frac{165}{15} = \frac{24}{15} x - \frac{75}{15}$

$15 \left[\frac{20}{15} x - \frac{165}{15}\right] = 15 \left[\frac{24}{15} x - \frac{75}{15}\right]$

$20 x - 165 = 24 x - 75$

$- 90 = 4 x$

$x = - 22.5$

So the x-coordinate is $- 22.5$. Let's plug that in to one of those two equations and find the y-coordinate:

$y = \frac{8}{5} x - 5$

$y = \frac{8}{5} \left(- 22.5\right) - 5$

$y = - 36 - 5$

$y = - 41$

So it looks like the point of intersection is $\left(- 22.5 , - 41\right)$

3

## Socratic Meta--what is it good for?

Stefan V.
Featured 20 hours ago · Socratic Meta

Socratic Meta is a place that the Socratic community can use to ask questions and find out more about how Socratic works and share thoughts and ideas on how it can be improved.

Think of Meta as our very own Town Hall -- a platform that allows us to discuss and promote the mission and the values of the community, to help each other navigate and make the most out of the features that Socratic offers.

In a nutshell, Meta is a place that we can use to grow as a community and as a site.

Moreover, Meta will provide contributors with a communication channel for getting in touch with the members of the Socratic team, as well as with moderators, heroes, and featured answers reviewers.

Every contributor is encouraged to use Meta to

• suggest new features or ways to improve the current ones
• ask for help or clarification about anything related to Socratic (the website and the app) or its community
• report inappropriate or abusive questions, answers, or users
• report bugs

In this regard, it's important to keep in mind that Meta is not a random discussion area, so please do not use Meta for discussion topics that are unrelated to Socratic.