Difference between revisions of "Apps-On-Physics/C3/Convex-Lenses/English"

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Line 17: Line 17:
 
|| At the end of this tutorial you will be able to,
 
|| At the end of this tutorial you will be able to,
  
−
Change the focal length and see the kind of image formed.
+
*Change the focal length and see the kind of image formed.
  
−
Change the object distance and object height and see the kind of image formed.
+
*Change the object distance and object height and see the kind of image formed.
  
−
Calculate the magnification and length of the telescope tube.
+
*Calculate the magnification and length of the telescope tube.
  
 
|-
 
|-
Line 29: Line 29:
 
|| Here I am using,
 
|| Here I am using,
  
−
Ubuntu Linux OS version 16.04
+
*Ubuntu Linux OS version 16.04
−
 
+
*Firefox Web Browser version 62.0.3
−
Firefox Web Browser version 62.0.3
+
  
 
|-
 
|-
Line 41: Line 40:
 
|| To follow this tutorial, learner should be familiar with '''Apps on Physics'''.
 
|| To follow this tutorial, learner should be familiar with '''Apps on Physics'''.
  
−
For the Pre-requisites tutorials please visit this site.
+
For the prerequisite tutorials please visit this site.
  
 
|-
 
|-
Line 53: Line 52:
 
|| In this tutorial we will use,
 
|| In this tutorial we will use,
  
−
'''Image Formation by Converging Lenses '''and  
+
*'''Image Formation by Converging Lenses '''and  
  
−
'''Refracting Astronomical Telescope Apps'''.
+
*'''Refracting Astronomical Telescope Apps'''.
  
 
|-
 
|-
−
|| Right click on '''imageconverginglens_en.htm''' file.
+
|| Right-click on '''imageconverginglens_en.htm''' file.
  
−
Select the '''Open With Firefox web Browser''' option.
+
Select the '''Open With Firefox Web Browser''' option.
  
 
Cursor on the '''App'''.
 
Cursor on the '''App'''.
−
|| Right click on '''imageconverginglens_en.htm '''file.
+
|| Right-click on '''imageconverginglens_en.htm '''file.
  
−
Select the '''Open With Firefox web Browser '''option'''.'''
+
Select the '''Open With Firefox Web Browser '''option.
  
−
'''Image Formation by Converging Lenses App''' opens in the browser.
+
'''Image Formation by Converging Lenses App''' opens in the '''browser'''.
  
 
|-
 
|-
Line 79: Line 78:
  
 
Show the ray diagram with all the positions.
 
Show the ray diagram with all the positions.
−
|| Before moving to the '''App''' let us first be familiar with a ray diagrams.
+
|| Before moving to the '''App''' let us first be familiar with a ray diagram.
  
 
Let us define principal axis.
 
Let us define principal axis.
Line 87: Line 86:
 
A vertical axis divides the lens into two equal halves.
 
A vertical axis divides the lens into two equal halves.
  
−
There are four positions on the principal axis, these positions are 2F , F , F’ and 2F’.
+
There are four positions on the principal axis.
 +
 
 +
These positions are 2F , F , F’ and 2F’.
  
 
F is the focal length and 2F is the twice the distance of focal length.
 
F is the focal length and 2F is the twice the distance of focal length.
  
−
F’ and 2F’ are on the opposite side of the lens with the same distance as F and 2F’.
+
F’ and 2F’ are on the opposite side of the lens with the same distance as F and 2F.
  
 
|-
 
|-
Line 141: Line 142:
 
|-
 
|-
 
|| Edit the '''Focal length''' to 20 '''cm''' and press '''Enter'''.
 
|| Edit the '''Focal length''' to 20 '''cm''' and press '''Enter'''.
−
|| Change the value of '''Focal length''' to 20 '''cm '''and press''' Enter'''.
+
|| Change the value of '''Focal length''' to 20 cm and press''' Enter'''.
  
 
|-
 
|-
 
|| Point to the radio buttons Principle light rays and Bundle of light rays.
 
|| Point to the radio buttons Principle light rays and Bundle of light rays.
−
|| At the bottom of the green panel there are two radio buttons.
+
|| At the bottom of the green panel, there are two radio buttons.
  
 
'''Principal light rays''' and '''Bundle of light rays'''.
 
'''Principal light rays''' and '''Bundle of light rays'''.
Line 155: Line 156:
 
|-
 
|-
 
|| Click on the drop down list.
 
|| Click on the drop down list.
−
|| A drop down is provided to '''Emphasize''' different parameters.
+
|| A drop-down is provided to '''Emphasize''' different parameters.
  
 
|-
 
|-
 
|| Click on the drop down and Select''' Object distance.'''
 
|| Click on the drop down and Select''' Object distance.'''
−
|| From the drop down list, select '''Object distance.'''
+
|| From the drop-down list, select '''Object distance.'''
  
 
|-
 
|-
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|| We can also change the object distance by dragging the object.
 
|| We can also change the object distance by dragging the object.
  
−
As we drag the value in the text-box changes accordingly.  
+
As we drag, the value in the text-box changes accordingly.  
  
 
|-
 
|-
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|-
 
|-
 
|| Point to the last ray which parallel to the optical axis after refraction.
 
|| Point to the last ray which parallel to the optical axis after refraction.
−
|| A third ray passes through the first principal focus F.
+
|| A third ray passes through the first principal focus.
  
−
This ray, after refraction is parallel to the principal axis.
+
This ray, after refraction, is parallel to the principal axis.
  
 
|-
 
|-
 
|| Point to show the meeting point of the rays.
 
|| Point to show the meeting point of the rays.
−
|| The image is formed, at point of intersection of the three rays.
+
|| The image is formed at point of intersection of the three rays.
  
 
|-
 
|-
 
|| Cursor on the interface.
 
|| Cursor on the interface.
 
|| Let us change the position of the object and see where the image appears.
 
|| Let us change the position of the object and see where the image appears.
−
 
  
 
|-
 
|-
Line 237: Line 237:
  
 
'''Image height.'''
 
'''Image height.'''
−
|| This is the condition for''' 2F''', when object is at''' 2F''' the image will appear at '''2F'''’.
+
|| This is the condition for''' 2F'''.
 +
 
 +
When object is at''' 2F''' the image will appear at '''2F'''’.
  
 
Here the object distance and height will be equal to image distance and image height.
 
Here the object distance and height will be equal to image distance and image height.
Line 255: Line 257:
 
|| Observe that the image is formed beyond '''2F’'''.
 
|| Observe that the image is formed beyond '''2F’'''.
  
−
The image formed is '''real''',''' inverted''' and '''magnified'''.
+
The image formed is '''real, inverted''' and '''magnified'''.
  
 
|-
 
|-
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|| Observe that image is formed at the first principal focus behind the object.
 
|| Observe that image is formed at the first principal focus behind the object.
  
−
Here the image formed is '''virtual''', '''upright''', and '''magnified'''.
+
Here the image formed is '''virtual, upright''', and '''magnified'''.
  
 
|-
 
|-
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|-
 
|-
−
|| To open the '''App''' right click on '''refractor_en.htm.  
+
|| To open the '''App''' right-click on '''refractor_en.htm.  
  
−
Select option '''Open with Firefox Web Browser.'''  
+
Select '''Open with Firefox Web Browser.'''  
−
|| To open the''' App''' right click on '''refractor_en.htm''' file.
+
|| To open the''' App''' right-click on '''refractor_en.htm''' file.
  
 
Select the option '''Open with Firefox Web Browser'''.
 
Select the option '''Open with Firefox Web Browser'''.
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|-
 
|-
 
|| Point the cursor to show the information.
 
|| Point the cursor to show the information.
−
|| Before moving to the simulation please read the information given on the screen.  
+
|| Before moving to the simulation, please read the information given on the screen.  
  
 
|-  
 
|-  
Line 307: Line 309:
 
|-
 
|-
 
|| Point to the bigger lens.
 
|| Point to the bigger lens.
−
|| In the yellow panel the bigger lens is the objective.  
+
|| In the yellow panel, the bigger lens is the objective.  
  
 
The objective has a large focal length.
 
The objective has a large focal length.
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|-
 
|-
 
|| Point to the smaller lens.
 
|| Point to the smaller lens.
−
|| Here the smaller lens is an Eyepiece.
+
|| Here the smaller lens is an '''Eyepiece'''.
  
 
|-
 
|-
Line 341: Line 343:
 
|-
 
|-
 
|| Highlight this sentence from the '''App'''(2nd para 1<sup>st</sup> line).
 
|| Highlight this sentence from the '''App'''(2nd para 1<sup>st</sup> line).
−
|| Here we can vary the '''Focal lengths '''of '''Objective''' and '''Eyepiece''' from 0.05 '''m '''to 0.5 '''m'''.
+
|| Here we can vary the '''Focal lengths''' of '''Objective''' and '''Eyepiece''' from 0.05 m to 0.5 m.
  
 
|-
 
|-
Line 349: Line 351:
  
 
Point to '''Magnification'''.
 
Point to '''Magnification'''.
−
|| As per the changes in the focal lengths,
+
|| As per the changes in the '''Focal lengths, App '''calculates '''Angles''' and '''Magnification'''.
−
 
+
−
'''App '''calculates '''Angles''' and '''Magnification'''.
+
  
 
|-
 
|-
 
|| Scroll down to see the formula for magnification.
 
|| Scroll down to see the formula for magnification.
−
|| At the bottom of the screen '''App''' has given the formula for magnification.
+
|| At the bottom of the screen, '''App''' has given the formula for magnification.
  
 
|-
 
|-
Line 363: Line 363:
 
'''v'''<nowiki>= - f</nowiki><sub>1</sub>/ f<sub>2 </sub>
 
'''v'''<nowiki>= - f</nowiki><sub>1</sub>/ f<sub>2 </sub>
  
−
Here v is the magnification
+
Here v is the '''Magnification'''
  
−
f<sub>1 </sub>is the focal length of Objective and  
+
f<sub>1 </sub>is the focal length of '''Objective''' and  
  
−
f<sub>2 </sub>is the focal length of Eyepiece.
+
f<sub>2 </sub>is the focal length of '''Eyepiece'''.
  
 
|-
 
|-
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|-
 
|-
−
|| Edit the value of '''Focal length''' of the '''Objective''' to 0.45 m  
+
|| Edit the value of '''Focal length''' of the '''Objective''' to 0.45 m and '''Eyepiece''' to 0.1 m.
−
 
+
|| Change the '''Focal length''' of '''Objective''' to 0.45 m and '''Eyepiece''' to 0.1 m.
−
and '''Eyepiece''' to 0.1''' m.'''
+
−
|| Change the '''Focal length''' of '''Objective''' to 0.45 '''m '''and '''Eyepiece''' to 0.1''' m.'''
+
  
 
|-
 
|-
 
|| Point to the observed value.
 
|| Point to the observed value.
−
|| Observe that '''App '''has calculated the value for magnification.
+
|| Observe that '''App '''has calculated the value for '''Magnification'''.
  
 
|-
 
|-
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|| Notice the changes in the black circle.
 
|| Notice the changes in the black circle.
  
−
If we increase the focal length of the Objective image will be more magnified.
+
If we increase the focal length of the '''Objective''', image will be more magnified.
  
 
|-
 
|-
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'''<nowiki>= 0.6 m</nowiki>'''
 
'''<nowiki>= 0.6 m</nowiki>'''
−
|| Formula to calculate the length of the telescope tube is sum of the focal lengths of objective and eyepiece.
+
|| Formula to calculate the length of the telescope tube is sum of the '''Focal lengths''' of '''Objective''' and '''Eyepiece'''.
  
 
That is: L= f<sub>1</sub> + f<sub>2.</sub>
 
That is: L= f<sub>1</sub> + f<sub>2.</sub>
  
−
Here f1 is focal length of Objective and f2 is focal length of Eyepiece.
+
Here f1 is focal length of '''Objective''' and f2 is focal length of '''Eyepiece'''.
  
−
Substitute the focal lengths and calculate the length of the telescope tube.
+
Substitute the '''Focal lengths''' and calculate the length of the telescope tube.
  
−
Observe that the length of the telescope is 0.6 '''m'''.
+
Observe that the length of the telescope is 0.6 m.
  
 
|-
 
|-
Line 442: Line 440:
 
'''Assignment'''
 
'''Assignment'''
  
−
An astronomical telescope has an objective of focal length
+
*An astronomical telescope has an objective of focal length 0.45 m and an eyepiece of focal length 0.25 m.
  
−
0.45 m and an eyepiece of focal length 0.25 m.  
+
*Find the magnification produced by the telescope.  
  
−
Find the magnification produced by the telescope.
+
*Verify the calculated value with the ones shown in the '''App.'''
−
 
+
−
Verify the calculated value with the ones shown in the App.'''
+
 
|| As an assignment solve this numerical.
 
|| As an assignment solve this numerical.
  
 
|-
 
|-
 
||  
 
||  
−
|| Let us summarise
+
|| Let us summarise.
  
 
|-
 
|-
Line 461: Line 457:
 
|| Using these '''Apps''' we have,
 
|| Using these '''Apps''' we have,
  
−
Changed the focal length and saw the kind of image formed.
+
*Changed the focal length and saw the kind of image formed.
  
−
Changed the object distance and object height and saw the kind of image formed.
+
*Changed the object distance and object height and saw the kind of image formed.
  
−
Calculated the magnification and length of the telescope tube.
+
*Calculated the magnification and length of the telescope tube.
  
 
|-
 
|-
Line 490: Line 486:
 
'''Spoken Tutorial workshops.'''
 
'''Spoken Tutorial workshops.'''
  
−
|| The&nbsp;'''Spoken Tutorial Project&nbsp;'''team,
+
|| The '''Spoken Tutorial Project '''team conducts workshops and gives certificates.
−
 
+
−
conducts workshops and gives certificates.
+
  
 
For more details, please write to us.
 
For more details, please write to us.

Revision as of 12:14, 6 May 2020

Visual Cue Narration
Slide Number 1

Title Slide

Welcome to the Spoken Tutorial on Convex Lenses.
Slide Number 2

Learning objective

At the end of this tutorial you will be able to,
  • Change the focal length and see the kind of image formed.
  • Change the object distance and object height and see the kind of image formed.
  • Calculate the magnification and length of the telescope tube.
Slide Number 3

System Requirements

Here I am using,
  • Ubuntu Linux OS version 16.04
  • Firefox Web Browser version 62.0.3
Slide Number 4

Pre-requisites

https://spoken-tutorial.org/

To follow this tutorial, learner should be familiar with Apps on Physics.

For the prerequisite tutorials please visit this site.

Point to the file in the downloads folder I have already downloaded Apps on Physics to my Downloads folder.
Slide Number 5

Apps on Physics

In this tutorial we will use,
  • Image Formation by Converging Lenses and
  • Refracting Astronomical Telescope Apps.
Right-click on imageconverginglens_en.htm file.

Select the Open With Firefox Web Browser option.

Cursor on the App.

Right-click on imageconverginglens_en.htm file.

Select the Open With Firefox Web Browser option.

Image Formation by Converging Lenses App opens in the browser.

Point to the convex lens in the App. The App shows a ray diagram of the convex lens.
Slide Number 6

Converging Lens Ray Diagram

Show the ray diagram with all the positions.

Before moving to the App let us first be familiar with a ray diagram.

Let us define principal axis.

It is an imaginary line passing through the optical center.

A vertical axis divides the lens into two equal halves.

There are four positions on the principal axis.

These positions are 2F , F , F’ and 2F’.

F is the focal length and 2F is the twice the distance of focal length.

F’ and 2F’ are on the opposite side of the lens with the same distance as F and 2F.

Open App. Now let us open the App.
Point to the scale at the bottom of the yellow panel. Let us use the scale to spot the positions of focal length F and 2F.
Point to show the Zero on the scale.

Point to Object distance.

Move the screen using the pressed mouse.

Initially the object is placed at the zero position of the scale.

The distance of the object from the lens is 50 cm.

The vertical black line beyond the lens is a screen.

This screen can be moved back and forth.

Point to the blue arrow. Blue arrow indicates the height of the object.

It is placed beyond 2F.

Point the cursor on 2F position. 2F is twice the distance of the focal length F.
Show it on the scale. From the App, the focal length is 10 cm, so position of 2F has to be at 20 cm.
Point to the green arrow. Green arrow indicates the image formed by the convex lens.
In the green control panel point to Focal length,

Object distance, and Object height.

In the green control panel we can edit the values of the following parameters.
Edit the Focal length to 20 cm and press Enter. Change the value of Focal length to 20 cm and press Enter.
Point to the radio buttons Principle light rays and Bundle of light rays. At the bottom of the green panel, there are two radio buttons.

Principal light rays and Bundle of light rays.

Point to Principal light rays. By default Principal light rays option is selected.
Click on the drop down list. A drop-down is provided to Emphasize different parameters.
Click on the drop down and Select Object distance. From the drop-down list, select Object distance.
Point to the object distance.

Point to blinking line.

Observe that the App emphasizes the object distance using a blinking line.

The blinking line disappears after sometime.

Drag the object(blue arrow) to show the changes in object distance. We can also change the object distance by dragging the object.

As we drag, the value in the text-box changes accordingly.

Press F5 key on the keyboard Press F5 key on the keyboard to refresh the App.
Edit the Object height to 15 cm and press Enter. Now change the value of Object height to 15 cm.

Change the Focal length to 20 cm.

Cursor on the ray diagram. Let us learn about the ray diagram.
Point to the ray which is parallel to the optical axis.

Point to the ray.

The ray emerging from the object is parallel to the principal axis of the lens.

This ray after refraction passes through the second principal focus F’.

Point to the second ray of light which passes without any deviation. A second ray of light passes through the optical center of the lens.

This ray after refraction emerges without any deviation.

Point to the last ray which parallel to the optical axis after refraction. A third ray passes through the first principal focus.

This ray, after refraction, is parallel to the principal axis.

Point to show the meeting point of the rays. The image is formed at point of intersection of the three rays.
Cursor on the interface. Let us change the position of the object and see where the image appears.
Edit the value of Object distance to 35 cm and Object height to 10 cm. Change the Object distance to 40 cm and Object height to 10 cm.
In the control panel point to the Kind of image formed.

real, inverted and equal dimension.

The Kind of image is real, inverted and equal dimension.
Point to show the values of following.

Object distance

Object height

Image distance

Image height.

This is the condition for 2F.

When object is at 2F the image will appear at 2F’.

Here the object distance and height will be equal to image distance and image height.

Drag the object between 2F and F.

Drag the object to 10 cm.

Drag the object between the 2F and F.

Drag the object to 10 cm.

Here we can use the scale to take the measurement.

Point to the image formed. Observe that the image is formed beyond 2F’.

The image formed is real, inverted and magnified.

Drag the object between F and optic center.

Drag it to 30 cm.

Drag the object between F and optic center.

Drag the object to 30 cm.

Point to the image (green arrow). Observe that image is formed at the first principal focus behind the object.

Here the image formed is virtual, upright, and magnified.

Slide Number 7

Assignment

As an assignment

Change the focal length of a convex lens to 10 cm and its object distance to 15 cm.

What characteristics of the image do you observe?

Cursor on the interface. Let us move on to next App.
To open the App right-click on refractor_en.htm.

Select Open with Firefox Web Browser.

To open the App right-click on refractor_en.htm file.

Select the option Open with Firefox Web Browser.

Point to the App. The App opens with a Refracting Astronomical Telescope.
Point the cursor to show the information. Before moving to the simulation, please read the information given on the screen.
Scroll down. Scroll down the screen.
Point to the bigger lens. In the yellow panel, the bigger lens is the objective.

The objective has a large focal length.

Point to the smaller lens. Here the smaller lens is an Eyepiece.
Point to the red coloured rays. The red coloured rays indicate the light from a distant object.
Move the cursor to show the path of the rays. Light rays from a distant object enter the objective lens.

After refraction a real image is formed at the second focal point.

Point to the eyepiece. Then the eyepiece magnifies the image.

The image formed is enlarged and inverted.

Point to the black circle which is at the bottom right corner. The magnified image of six brightest star of the pleiades is seen in the black circle.
In the green control panel point to Focal length of Objective and Eyepiece. In the green panel, Focal lengths of Objective and Eyepiece can be edited.
Highlight this sentence from the App(2nd para 1st line). Here we can vary the Focal lengths of Objective and Eyepiece from 0.05 m to 0.5 m.
Point to the Angles

Objective and Eyepiece.

Point to Magnification.

As per the changes in the Focal lengths, App calculates Angles and Magnification.
Scroll down to see the formula for magnification. At the bottom of the screen, App has given the formula for magnification.
Point to the formula. That is:

v= - f1/ f2

Here v is the Magnification

f1 is the focal length of Objective and

f2 is the focal length of Eyepiece.

Let us calculate the magnification using the data from the App.
Edit the value of Focal length of the Objective to 0.45 m and Eyepiece to 0.1 m. Change the Focal length of Objective to 0.45 m and Eyepiece to 0.1 m.
Point to the observed value. Observe that App has calculated the value for Magnification.
Point to the black circle. Notice the changes in the black circle.

If we increase the focal length of the Objective, image will be more magnified.

Let us now calculate the length of the telescope tube.
Press F5 key on the keyboard. Change the Focal lengths of the Objective and Eyepiece to their default values.

Press F5 key on the keyboard to restart the App.

Slide Number 8

Telescope Tube

Length of the tube is sum of the focal lengths

of objective and eyepiece.

L= f1 + f2

= 0.50 + 0.10

= 0.6 m

Formula to calculate the length of the telescope tube is sum of the Focal lengths of Objective and Eyepiece.

That is: L= f1 + f2.

Here f1 is focal length of Objective and f2 is focal length of Eyepiece.

Substitute the Focal lengths and calculate the length of the telescope tube.

Observe that the length of the telescope is 0.6 m.

Edit the values of Focal length of Objective to 0.1 m

and Eyepiece to 0.5 m.

Now reverse the Focal lengths of the Objective and Eyepiece.
Point to the single dot in the second black circle. Observe that the six brightest stars of pleiades appear to be a single point.
This is because the focal length of the Objective is smaller than that of the Eyepiece.
Slide Number 9

Assignment

  • An astronomical telescope has an objective of focal length 0.45 m and an eyepiece of focal length 0.25 m.
  • Find the magnification produced by the telescope.
  • Verify the calculated value with the ones shown in the App.
As an assignment solve this numerical.
Let us summarise.
Slide Number 10

Summary

Using these Apps we have,
  • Changed the focal length and saw the kind of image formed.
  • Changed the object distance and object height and saw the kind of image formed.
  • Calculated the magnification and length of the telescope tube.
Slide Number 11

Acknowledgement

These Apps are created by Walter-fendt and his team.

These Apps are created by Walter-fendt and his team.
Slide Number 12

About Spoken Tutorial project.

The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

Slide Number 13

Spoken Tutorial workshops.

The Spoken Tutorial Project team conducts workshops and gives certificates.

For more details, please write to us.

Slide Number 14

Forum for specific questions:

Please post your timed queries in this forum.
Slide Number 15

Acknowledgement

The Spoken Tutorial Project is funded by MHRD, Government of India.
This is Himanshi Karwanje from IIT-Bombay.

Thank you for joining.

Contributors and Content Editors

Karwanjehimanshi95, Madhurig, Nancyvarkey

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