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Solid State Chemistry Questions and Answers – Intensities

This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Intensities”.

1. Intensities of X-ray reflections is important because___________
a) The quantitative measurements of intensity are neccasary
b) X-ray is detected using intensity
c) Intensity is required during determining the concentration
d) The environmental condition is suited using intensities
View Answer

Answer: a
Explanation: Intensities of X-rays are important for two main reasons. First, quantitative measurements of intensity are necessary in order to determine unknown crystal structures. Second, qualitative or semi-quantitative intensity data are needed in using the power fingerprint method to characterize materials and especially in using the powder diffraction file to identify unknowns.

2. Atoms diffract or scatter X-rays because of__________
a) Incident visible light
b) Incident X-ray beam
c) Incident gamma ray
d) Incident electrons
View Answer

Answer: b
Explanation: An Atom diffract or scatter X-rays because of incident X-ray beam which can be described as an electromagnetic wave with an oscillating electric field, sets each electron of an atom into vibration.

3. The electrons of an atom act as which of the following options for the sources of X-rays?
a) Electrode
b) Primary source
c) Secondary source
d) Tertiary source
View Answer

Answer: c
Explanation: A vibrating charge such as an electron emits radiation and this radiation in in phase or coherent with the incident X-ray beam. The electrons of an atom therefore act as the secondary point sources of X-rays.

4. The intensity of the radiation scattered coherently by ‘point source’ electrons has been treated theoretically and is given by which of the following equations?
a) Einstein equation
b) Maxwell equation
c) Stockbarger equation
d) Thomson equation
View Answer

Answer: d
Explanation: Thomson equation is given by:-
I_p α ½( 1+ cos²2Θ)
Here, I_p is the scattered intensity at any point P, and 2Θ is the angle between the directions of the incident beam and the diffracted beam that passes through P, from this equation it can be seen that the scattered beams are most intense when parallel or antiparallel to the incident beam and the weakest when at 90˚ to the incident beam.

5. Thomson equation is also known as _________
a) Diffraction factor
b) Reflection factor
c) Polarization factor
d) Thomson factor
View Answer

Answer: c
Explanation: The Thomson equation which is used to measure the intensity of the radiation scattered coherently by ‘point source’ electrons is also known as polarization factor and is one of the standard angular correction factors that must be applied during the processing of intensity data (for use in structure (determination).

6. For the non-crystalline beams are scattered by the atoms _________
a) From top to bottom
b) In horizontal direction
c) In vertical direction
d) In all direction
View Answer

Answer: d
Explanation: Each atom in a material acts as a secondary point source of X-rays. If the material is non-crystalline, beams are scattered by the atoms in all directions, but in crystalline materials the scattered beams interfere destructively in most possible directions.

7. Intensities depends on which of the following factors?
a) Solubility of the solid
b) Emission factor
c) Refraction factor
d) Absorption factor
View Answer

Answer: d
Explanation: Intensities depend on several factors, one of its factor is absorption factor, absorption of X-rays by the sample and depend on the form of the sample and geometry of the instrument. Ideally, for single crystal work, crystals should be spherical so as to have the same absorption factor in all directions.

8. An electron density is a plot of variation of ______
a) Electron density
b) Electron solubility
c) Electron mass
d) Electron volume
View Answer

Answer: a
Explanation: A plot of variation of electron density throughout the unit cell is known as electron density map. During the process of the solving an unknown structure it is often useful to construct electron density maps in order to try and locate atoms.

9. An electron map resembles which of the following options?
a) Electron spectrum
b) Geographical contour map
c) Diffraction spectrum
d) Resolution electron map
View Answer

Answer: b
Explanation: An electron map resembles a geographical contour map. The contours represent lines of constant electron density throughout the structure. Peaks of the electron density maxima may be distinguished clearly and these correspond to the atoms, the coordinates of the atoms in the unit cell are given by the coordinates of the peak maxima.

10. The mental picture of atom is sphere can be given by which of the following?
a) Pauli exclusion principle
b) Maxwell equation
c) Electron density map
d) Stockbarger equation
View Answer

Answer: c
Explanation: Electron density maps also show that our mental picture of atoms as spheres is essentially correct, at least on a time average. The electron density drops to almost zero at some point along point along the line connecting pairs of adjacent atom and this supports the model of ionic bonding in NaCl.

Sanfoundry Global Education & Learning Series – Solid State Chemistry.

To practice all areas of Solid State Chemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Python | Convert case of elements in a list of strings

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Given a list of strings, write a Python program to convert all string from lowercase/uppercase to uppercase/lowercase.

Input : ['GeEk', 'FOR', 'gEEKS']
Output: ['geeks', 'for', 'geeks']

Input : ['fun', 'Foo', 'BaR']
Output: ['FUN', 'FOO', 'BAR']

Method #1 : Convert Uppercase to Lowercase using map function

out = map(lambda x:x.lower(), ['GeEk', 'FOR', 'gEEKS'])

output = list(out)

print(output)

Output:


['geek', 'for', 'geeks']

Method #2: Convert Lowercase to Uppercase using List comprehension

input = ['fun', 'Foo', 'BaR']

lst = [x.upper() for x in input]

print(lst)

Output:


['FUN', 'FOO', 'BAR']

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Java String Array to String Example

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Java String Array to String Example

This Java String Array to String Length example shows how to convert String array to

Java String object.

import java.util.Arrays;

public class StringArrayToStringExample {

public static void main(String args[]){

//String array

String[] strArray =

new String[]{“Java”, “String”, “Array”, “To”, “String”, “Example”};

* There are several in which we can convert String array to

* String.

* 1. Using Arrays.toString method

* This method returns string like [element1, element2..]

String str1 = Arrays.toString(strArray);

//replace starting “[” and ending “]” and “,”

str1 = str1.substring(1, str1.length()–1).replaceAll(“,”, “”);

System.out.println(“String 1: “ + str1);

* 2. Using Arrays.asList method followed by toString.

* This method also returns string like [element1, element2..]

String str2 = Arrays.asList(strArray).toString();

//replace starting “[” and ending “]” and “,”

str2 = str2.substring(1, str2.length()–1).replaceAll(“,”, “”);

System.out.println(“String 2: “ + str2);

* PLEASE NOTE that if the any of the array elements contain “,”, it will be

* replaced too. So above both methods does not work 100%.

//3. Using StringBuffer.append method

StringBuffer sbf = new StringBuffer();

if(strArray.length > 0){

sbf.append(strArray[0]);

for(int i=1; i < strArray.length; i++){

sbf.append(” “).append(strArray[i]);

}

System.out.println(“String 3: “ + sbf.toString());

}

Output of above example would be

String 1: Java String Array To String Example

String 2: Java String Array To String Example

String 3:Java String Array To String Example

14. Two-way data binding with v-model

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Finally, the day has come, to understand the missing piece of the puzzle, data binding. So far, we have seen how to use interpolations, v-bind for attribute binding and v-on to listen to events. The missing piece was v-model which is used for two-way data binding and this is exactly what we will be concentrating on today!

Big word alert!

Two-way data binding: This is just a relation between the model (data object in the Vue instance) and the view. Any change made in the view (say, by the user) will immediately be reflected in the underlying Vue model and will be updated at all places where this data is being rendered in the view. In other words,

View is updated with the change made to the data property (model)
And, the data property (model) is updated whenever a change is made in the view

Is your head spinning yet? No worries! We will understand this concept by walking through an example.

v-model directive

This two-way binding is usually created with form inputs and controls. And v-model is the directive used to achieve just that! To be more specific, below are the exact HTML elements with which v-model is used,

<input>
<textarea>
<select>
Components (we will be covering this topic in the “Advanced VueJS” section)

Example walkthrough

Let us take an example with <input> element to show a text field on the webpage. Let us also have a “message” property in the Vue instance’s data object which acts as our Vue model and a <p> tag to render the value using mustache syntax (text interpolation). Now, we want to,

Populate the text field with the message property’s value, say, “hi” i.e., updating the view with the model.
Whenever the value, “hi” is changed by the user in the text field, it has to be updated in the data property, message in our case i.e., updating the model with changes in view and
Also rendering it in the <p> tag simultaneously

All these three steps can be done by adding the v-model directive to the <input> tag and binding the “message” property to it like so,

<input type="text" v-model="data_property_to_bind"></input>

Index.html

<!DOCTYPE html>
<html>
  <head>
    <title>Hello Vue!</title>
    <!-- including Vue with development version CDN -->
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  </head>
  <body>
    <div id="app">
      <h2>Welcome</h2>
      <div>
        <!-- two-way binding with v-model -->
        Greeting Message:
        <input type="text" v-model="message"></input> 
        <p>The message is: {{ message }}</p>
      </div>
    </div>
    <!-- including index.js file -->
    <script src="index.js"></script>
  </body>
</html>

Index.js

new Vue({
  el: "#app",
  data: {
    message: "hi"
  }
});

So, the v-model directive tells vue.js to set up a two-way binding for the input field and the message data property mentioned within the quotation marks. All this happens reactively of course!

The initial output is as below.

v-model initial output

The right half in the image shows Vue DevTools pane. The data object with the message property and its value can also be seen.

As we change the message in the text field from “hi” to “hello”, with every character that we type, it will reactively get updated in the underlying data model (shown in the Vue Devtools) and updated in the view where we output using mustache syntax in the <p> tag.

reactivity with v-model

I highly recommend you to open Vue Devtools as shown in the image and change the value in the text field to see this change happening reactively. It will be a feast to your eyes! I can assure that.

Modifiers

v-model comes with three modifiers. In case you missed the modifiers part, check this out.

Usage: Following the v-model directive, add a dot and specify the modifier.

.lazy– sync the input with the data after change events instead of input events

<input v-model.lazy="message">

.number– used to cast valid input string to numbers

<input v-model.number="age">

.trim– to trim the user input automatically

<input v-model.trim="message">

The code is available in the GitHub repo as always.

Play around with that and notice how Vue correctly updates the element based on whether the input type is a text field, checkbox, radio button, select, multi-select, text area element and so on… It looks and sounds magical because all the syntax sugar you need to achieve this elephant-sized task is a single directive, v-model. Feel free to give a shout out in the comments section in case you bump into any issues.

Have a great day ahead!

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Solid State Chemistry Questions and Answers – Modern X-Ray Powder Techniques and their Applications

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This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Modern X-Ray Powder Techniques and their Applications”.

1. A powder diffractometer is an___________
a) Electron density instrument
b) Powder electron refraction instrument
c) X-ray spectrum detector instrument
d) Powder X-ray instrument.
View Answer

Answer: d
Explanation: The most commonly used powder X-ray instrument is the powder diffractometer. It has a proportional, scintillation or Geiger counter as the detector which is connected to a chart recorder or sometimes to a means of digital output.

2. In the powder diffractometer, the counter is set, the counter is set to scan at a ________
a) Variable temperature
b) Constant temperature
c) Constant angular velocity
d) Variable angular velocity
View Answer

Answer: c
Explanation: In normal use, the counter in the powder diffractometer is set to scam over a range of 2Θ values at a constant angular velocity, it is common practice to refer to the angle 2Θ between the diffracted and undiffracted beams, rather than to the Bragg angle, Θ.

3. The intensities in the powder diffractometer is taken as________
a) very low height
b) peak height
c) constant height
d) variable height
View Answer

Answer: b
Explanation: In the powder diffractometer, the intensities are taken as peak height, unless very accurate work is being done, in which case areas may be measured, the most intense peak is given the intensity of 100 and the rest are scaled accordingly.

4. In the powder diffractometer, a correction factor varies with which of the following factors?
a) Temperature
b) Solubility
c) Concentration
d) Angle 2Θ
View Answer

Answer: d
Explanation: A correction factor in the powder diffractometer varies with 2Θ, is obtained from the discrepancy between observed and the true d-spacings of the standard and is then applied to the pattern that is being measured.

5. Which of the following phenomenon takes place when the arrangement of the crystal is not random?
a) The temperature increases
b) The temperature decreases
c) Preferred orientation exits
d) Preferred orientation enters
View Answer

Answer: c
Explanation: If the crystal arrangement is not random, then preferred orientation exists and can introduce errors, sometimes very large, into the measured intensities preferred orientation is a serious problem for the materials that crystallize in a characteristic, very non-spherical shape like clay minerals, etc.

6. Which one of the following is the big disadvantage of the Debye-Scherrer cameras?
a) High intensity diffracted beams
b) High intensity refracted beams
c) Low intensity refracted beams
d) Divergent diffracted beams
View Answer

Answer: d
Explanation: The big disadvantage of early Debye-Scherrer cameras is that incident and diffracted beams are inevitable, somewhat divergent and of low intensity. In diffractometer and the modern focusing cameras, a convergent X-ray beam is used.

7. Using the convergent X-ray in powder diffractometer which of the following factor is affected?
a) Temperature
b) Reflection
c) Resolution
d) Concentration
View Answer

Answer: c
Explanation: In diffractometer and the modern focusing cameras, a convergent X-ray beam is used, this gives a dramatic improvement in resolution and because much more intense beams may be used, exposure time ate greatly reduced.

8. Which one of the following is an additional feature of the focusing cameras?
a) X-ray
b) Crystal monochromator
c) Gamma rays detector
d) Electron stopper
View Answer

Answer: b
Explanation: In the focusing cameras an additional feature is the crystal monochromator which serves two functions, to give highly monochromatic radiation and to produce an intense, convergent X-ray beam.

9. A crystal monochromator contains which of the following material?
a) X-ray beam detector
b) A very small crystal
c) Crystal electrode
d) Large single crystal
View Answer

Answer: d
Explanation: A crystal monochromator consists of a large single crystal of for example quartz oriented such that one set of planes which diffracts strongly for quartz is at the Bragg angle to the incident beam.

10. For the accurate measurement of the d-spacings which of the following method is best to use?
a) Stockbarger method
b) Refractometry method
c) Diffractometry method
d) Dalton method
View Answer

Answer: b
Explanation: In order to measure the d-spacings accurately, Diffractometry is normally regarded as the best method and most of the patterns in the powder diffraction file gave been obtained by the Diffractometry. An internal standard of accurately known d-spacings must be added to the sample in order to eliminate the instrumental error.

Sanfoundry Global Education & Learning Series – Solid State Chemistry.

To practice all areas of Solid State Chemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Java String Array Contains Example

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Java String Array Contains Example

This Java String Array Contains example shows how to find a String in

String array in Java.

import java.util.Arrays;

public class StringArrayContainsExample {

public static void main(String args[]){

//String array

String[] strMonths = new String[]{“January”, “February”, “March”, “April”, “May”};

//Strings to find

String strFind1 = “March”;

String strFind2 = “December”;

* There are several ways we can check whether a String array

* contains a particular string.

* First of them is iterating the array elements and check as given below.

boolean contains = false;

//iterate the String array

for(int i=0; i < strMonths.length; i++){

//check if string array contains the string

if(strMonths[i].equals(strFind1)){

//string found

contains = true;

break;

}

if(contains){

System.out.println(“String array contains String “ + strFind1);

}else{

System.out.println(“String array does not contain String “ + strFind1);

}

* Second way to check whether String array contains a string is to use

* Arrays class as given below.

contains = Arrays.asList(strMonths).contains(strFind1);

System.out.println(“Does String array contain “ + strFind1 + “? “ + contains);

contains = Arrays.asList(strMonths).contains(strFind2);

System.out.println(“Does String array contain “ + strFind2 + “? “ + contains);

}

Output of above given Java String Array Contains example would be

String array contains String March

Does String array contain March? true

Does String array contain December? false