Test Papers – ICSE – Class – X
State Board Std X Science-Physics Demo Videos
Hello, students, welcome to the world of astrophysics. We live in this universe which is huge, isn’t this really, really beautiful. But, students, when you look at this universe I think there is one thing missing. Of course, the stars are not twinkling, so let’s make them twinkle. So here we have the stars twinkling.
Students, when you were in kindergarten you studied this poetry, this wonderful poetry, ‘Twinkle, twinkle little star. How I wonder what you are’. So let’s put that query to rest and understand how starts twinkle or why do stars twinkle? To understand this the first thing we need to understand is stars are point source of light. Now why are they point source of light, is because they are very, very far away from us, and as they are very far away, we use a unit to measure that is called Light Year.
Now, students, what is Light Year? Light Year is the distance travelled by light in one year. Now can you imagine light is so fast. The distance travelled by light in one year is 6 trillion miles. Let’s take an example of the closest star. The closest star is Alpha Centauri, and this closest star Alpha Centauri is at a distance of 4.22 light years, so you can imagine how far is the closest star to us. And as the stars are very far away they are considered as a point source of light.
Now let’s go to the actual understanding and see why stars twinkle. Now students we know that earth is surrounded by atmosphere. Now let us look at this atmosphere, the lower layer of the atmosphere is denser and as we go up, the air becomes rarer and rarer. So I can say the topmost layer is rarer and as we come down the air becomes less rarer and less rarer. So these are the different layers of atmosphere. Now, students, when you look at the star, the light from the star comes and now this light has to pass through different layers of atmosphere. So at every layer I will make a normal, now we know that when light travels from rarer to denser it bends towards the normal. So you can see here the light is bending towards the normal and the second layer once again I make a normal, once again the light will bend towards the normal, and in this way the light takes a curved path and enters the observer’s eye. Now when it comes into my eyes we don’t see curved, we see straight, so when I am looking I will feel the light is coming from this point. So the previous position where the star was is called the real position and now the place where I see the star is the apparent position of the star. So, students, when you look at the stars in the sky what you see is the apparent position of the star.
Now, students, the atmospheric condition is continuously changing because the seasons are changing. In rainy season the climatic conditions are different. In summer season the climatic conditions are again different. And oh, in winter season the climatic conditions are so different. Now because of this changing climatic condition, the atmospheric condition also changes. Now as the climatic condition is changing the intensity of light from the star coming into my eyes is also changing. So you can see the star becomes dim and then it becomes bright. Now as less light comes from the star, the star becomes dim, again more light comes and the star becomes bright and this effect of dim and bright to our eyes appears as twinkling of stars. So, students, twinkling is nothing but appear and disappear effect. And this was the understanding of how stars twinkle.
Students, this is a very important concept from exam point of view. So if this comes in exams, how do we write the points. First point, stars are point sources of light as they are very far away. The second point we write is, the refractive index of air in the given region in atmosphere goes on changing continuously and randomly. Now when the light refracts more light towards us the star is seen bright. Now when the atmosphere refracts less light towards us, the star is seen dim. Thus due to change in refractive index of atmosphere, stars appear twinkling at night. So these are the points of answer.
Thank you.
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State Board English Std X English Demo Videos
Hello, students, this is Nilofer, and let us start with the activities of another lesson that is ‘A Long Rally Ahead’. As you all know this lesson tells us about journey of Saina Nehwal through sports, her journey through sports. Let us start with the activities.
Pre-reading skills: Read the text carefully and select proper alternative from the following:
Let us see, the first line, the title ‘A Long Rally Ahead’ refers to Saina’s journey of life, journey of education or journey in sports. As we all know this lesson is an appreciative write up about Saina’s journey in sports, right. And rally, it’s name itself says it is a journey, okay.
Let us see, the theme of the text is qualities of a player, qualities of Saina as a player or how to play. As we all know that this is a write up about Saina Nehwal, right.
The tone of the write up is, appreciative, critical or satirical. It is appreciative. Mr. Padukone very beautifully describes her quality, right, that how she is excellent in everything, in the sports that she is pursuing, right. Okay, next.
The language of the write up is easy to understand, complex or literary. He hasn’t used any literary words, right, the write up is really very easy. Okay, next.
The presenter of the write up is the first person, the second person, the third person. Right, let us understand this, it is the third person as Mr. Padukone is writing about Saina Nehwal, he is the third person telling about Saina Nehwal, right. So here ‘I’ when he speaks ‘I’, right, he is referring to himself, so he is the third person writing the write up.
Okay, next, 7th activity, paragraph and summarizing. Write a title that sums up the paragraph, (one is done for you). Now let us see, this is the paragraph that is given to us.
Saina is exceptional, this paragraph, she is exceptional, she is technically fit and mentally fit, right. So we will give the title ‘Mental and physical qualities of Saina, okay. This paragraph describes her mental and her physical capabilities, right.
Next, personally I have …..well as tournaments. So this is actually applauding Indian women in sports, right. This is describing or saying that it is Indian women who are in the forefront in sports field, right.
Okay, next. Even though….on her defence as well. Here scope of improvement, though he is appreciating Saina’s qualities as a sportswoman she also has some scope for improvement. He is actually defining the forehand side that she should improve on her forehand side, okay.
Next, full credit ….. behind the scenes. He is giving all her team, her team of coach, right, her physiotherapist and all other persons behind the scenes, right, so he is crediting them for her success, right.
Okay, great. Now activity 8: True or False. State whether the following statements are true or false:
- Saina Nehwal consistently performed for four weeks. False.
Here we have the correct answer. It is, personally it has been three great weeks of consistent performance, right. Next.
- Saina Nehwal is different from other players because she has all the two qualities of a player. Are there two qualities? False. There are three. So here we have the line which says ‘Abundance of all the three attributes is vital, can be in the best of in the world’. Okay, next.
- Another great quality of Saina is her self belief and never-say-die attitude. True.
It is her self belief and never-say-die attitude that keeps her going, right. Next.
- While playing Saina depends on her low serves. True.
Here we have the line which says, ‘She has started depending mentally on her low serves’, okay. Next.
- Full credit to her coach, Pullela Gopichand. True.
She has given full credit to her coach, Pullela Gopichand, right, okay.
So with this we end the module here. Thank you.
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State Board English Std X Geography Demo Videos
Hello, students, welcome back. In this module we will gather information about the physiography of Himalayas, that is the North South Division of Himalayas. Now the Himalayas are the world’s highest mountain ranges, and they consist of four parallel ranges from south to north. The southernmost and the lower most range of the Himalayas is the Shiwalik Range. Beyond that we have the Lesser Himalayas which is also called as the Himachal Range. Beyond the Lesser Himalayas we have the Great Himalayas and they are also called as the Himadri Range. Beyond the Great Himalayas we have the Trans Himalayan Ranges. So we can see that Himalayas consist of four parallel ranges from south to north and they are the Shiwalik, the Lesser Himalayas, the Great Himalayas and the Trans Himalayas.
Now how are these parallel ranges formed? We have learnt that when the Indo-Australian Plate collided with the Eurasian plate, the sediments which were there at the bottom of the sea of the Tethys folded to form the Himalayan mountain ranges. But, my dear students, it was not one fold, the folds were multiple. So when the collision happened, the very first fold of the mountain was the lowermost fold and that is the Shiwalik mountain range. Beyond that the second fold was the Lesser Himalayas of a greater height. Beyond that we had the Great Himalayas which was of a still more height. And beyond that whatever mountain ranges were folded and formed they were together called as the Trans Himalayas. When we say ‘Trans’ it means beyond, so all the mountain ranges beyond the main Himalayan belt that is the Shiwalik, Lesser and Great Himalayas are together grouped and called as Trans Himalayas. So the Himalayan mountain ranges are four parallel ranges, the Shiwalik Range, the southernmost range, then the Lesser Himalayas, then the Great Himalayas and beyond that they are called as the Trans Himalayas.
So let us begin with the very first and the southernmost range which is the Shiwalik Mountain Range. The southernmost range of the Himalayan system is known as the Shiwalik Mountain range. The average altitude of the Shiwalik range varies between 900 to 1100 meters. The area between the Shiwalik and the Lesser Himalayas consist of a number of valleys. Now you will be wondering what do you mean by a valley, a low area of land between hills and mountains is called as a valley. As you can see very clearly in the picture here, the low lying area between two mountain ranges, this area is called as a valley. So we have similar valleys between the Shiwalik and the Lesser Himalayas. These valleys are more or less parallel to the mountain ranges. As you can see here, we have one mountain range and then the second mountain range. We have both the ranges running parallel and we have parallel longitudinal valleys. So such kind of longitudinal valleys exist between the Shiwalik and the Lesser Himalayas. Such valleys are called as Duns in the local language. There are many such examples of Dun valley, for example the Kotli Dun, Dehradun which is a very famous tourist destination, and also Patli Dun, these three are examples of Dun Valleys. The Shiwaliks as you can very clearly see in the map here are very clearly visible in the western side, but as we look towards the east they become less obvious means they are less visible in the Eastern Himalayas. Why, because in the eastern part which you can see the area which is highlighted in red, these mountain ranges almost merge with the Lesser Himalayas.
Now there is one important feature which we find at the foothill of the Shiwalik ranges, and this feature is nothing but the Alluvial Fans. What do you mean by the Alluvial Fans, what are these Alluvial Fans? These are unconsolidated heaps of sediments abruptly deposited by the rivers while entering the plains. Now when we say unconsolidated, it means loose sediments. There are many rivers which originate from the Himalayas and they enter the north Indian plain. While travelling from the Himalayas they do a very important work of erosion, they bring in a lot of sediments, they bring in a lot of alluvium with them. In the mountainous region when the rivers are flowing, they flow in a very restricted area which is called as a gorge. Now what do you mean precisely by a gorge? A deep narrow valley with steep sides, usually formed by a river or stream cutting through the hard rock. So when the rivers originate from the mountain, they break the parts of the mountain, they create a path for themselves. This restricted narrow path created by the river between the mountain is called as a gorge. So the rivers travel in a very restricted area which is a gorge. But as soon as they enter the plain it is a wide area. So the river water spreads abruptly, also the alluvium brought by the river also spreads abruptly here. And these features that we find at the foothills of the Shiwalik are called as Alluvial Fans. Now why do we call it as Alluvial Fans? Because they are created by the deposition of alluvium brought by the rivers and they have a structure or a shape of a fan.
We will continue with Lesser and the Great Himalayas in the next module.
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State Board English Std X Science Demo Videos
Welcome, students, to the next module of this chapter. Let us go further and learn more about the process of nutrition in human beings.
Beginning with the first part, we all know that the nutrition, that the process of nutrition in human beings takes place in a very special system called as the digestive system. And alimentary canal forms an integral part, forms the main part of the digestive system, and the alimentary canal begins with the mouth. So in other words we can say nutrition in human beings begins with mouth. So let’s find out more about it. Let’s focus on an aspect, dear students, we eat a variety of food items which have to pass through the same digestive track. The food that we eat has a lot of substances in it. And out of these some are hard while some are soft, the hard ones may cause damage to our highly muscular alimentary canal. So then naturally the food has to be first processed to generate particles with small size. Let’s see how does this happen in the mouth.
Okay, now we begin with the process of nutrition in the mouth. We all know we eat food in the form of tiny morsels, in the form of tiny bites. Now the food is taken in through the mouth, okay. Once inside the mouth the food is processed to generate particles with small size. And who helps us to do this, the natural mixers present in our mouth called as the teeth. They do the process of chewing by which the food that we eat is broken down into particles with small size. Furthermore, when the teeth are chewing the food, the salivary glands are stimulated and they secrete saliva into the mouth. The crushed food is wetted with saliva, now what happens because of this. The crushed food is converted into a soft mass that can pass easily through the soft lining of the alimentary canal without damaging it.
So let’s focus once more what all is happening, okay, as we all know, as we can see in the animation behind me, in the image behind me, saliva is completely getting mixed with the food, the food is being completely wetted by the saliva. Okay, once again the food that we eat is in the form of tiny morsels or bites, it is going to be chewed by teeth into particles of smaller size. Simultaneously, saliva is going to be mixed into it, and the food is going to be converted into a soft mass that can easily pass through the lining of the alimentary canal.
Furthermore, dear students, while this process of mechanical digestion that means breaking the food into tiny particles is taking place, one more important event is happening in the mouth. We cannot see it because it is inconspicuous because it is a chemical reaction that is happening. How and who helps us? The saliva contains an enzyme, this enzyme is called as salivary amylase. Focus on the name, dear students, salivary amylase, amylase any enzyme that has ‘ase’ as a suffix is definitely going to break down something in our body. And what is it going to break down? It is going to break down amyl, amyl means starch, amyl means carbohydrates. So, salivary amylase in the saliva acts on one of the major components of the food called as starch. The starch is acted upon by this enzyme and it is broken down into comparatively a simpler substance called as Maltose. Maltose is comparatively a simpler sugar, a disaccharide. Now, so in other words can we say, starch, a complex sugar, present in our food is acted upon by salivary amylase and is broken down into comparatively simple sugar called as maltose in the mouth. Does it tell us that food is partly digested in our mouth? In other words, can you also say the digestion of food starts in the mouth, the process of digestion begins in the mouth.
Dear students, this is a very important give reason for two marks which can come in a paper.
With this information we end this informative module and also the process of digestion.
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State Board English Std X Geometry Demo Videos
Hi, students, in this module from the chapter 4 of Trigonometry, lets learn the application of Trigonometry.
Now students, we have already learnt the ratios of Trigonometry, right, now when is this Trigonometry going to be applied in real life that is what we are going to learn now, observe now. So for this we are going to take a few examples. Now observe, there is a person here, and standing and watching Mount Everest and he is wondering something. He is thinking, what is the height of Mount Everest, and the next is how will I measure it. The question is, is he going to take a measuring tape, fix one end to the top and take the next end to the bottom and measure it. No, it is not possible that means it is impossible to measure it with the help of a measuring tape, isn’t it. The same way you observe this, now there is a person here, there is a boy standing here and observing this river, and he is thinking what is the width of this river, right. Is he going to take a measuring tape and do the same thing like that person did. No, it cannot be, it is impossible to do it with the help of a measuring tape to get the width of the river, right.
In the same way, here you have a couple standing and observing Eiffel Tower, right, and they are conversing between themselves. They are saying, yeah, it is looking beautiful, right. Yes, she says, yes, it is looking beautiful. But I am wondering what is its height? He is saying, oh, yeah, what is its height, how do we measure it. The same question they have. They are not again going to take the help of a measuring tape, it cannot be done, that means it is impossible to do it with the help of a measuring tape. So in all these three cases when you look, like the first case where we saw the height of the Mount Everest, second case when we talk about the width of the river and third case when we talk about the height of the Eiffel Tower. All such big heights and distances can be actually practically taken and we can find it out with the help of applying trigonometry. So application that is real application of trigonometry.
And if we have to learn this, students there are a few terms which we need to know, very important terms. There are basically four terms, first term is line of vision, second is horizontal line, third is angle of elevation and fourth is angle of depression. Now for this we have got a friend of ours and he is Raj, he is going to help us, he is saying, yeah, hi, I am going to help you to learn all the four terms, let’s understand. He is going to help us with the first term here, observe. So here comes Raj and what is he observing, he is observing a cow. So when he is observing a cow here, this person Raj becomes the observer and this cow becomes the object. When this observer is observing the object, there is a line passing through his eye connecting to that object. This imaginary line which connects the eye of the observer to the object is called Line of Vision. So that means the moment an observer observes an object there is a straight line passing through his eye to that object, that straight line is called as ‘Line of Vision’. Beautiful isn’t it, so easy.
In the same way, let’s see Raj is going to observe something more, what is he observing. Yes, this time see he is seeing the door of that tree house, see he is seeing the door of the tree house, he is seeing that. So now Raj is observer, that door is the object. So, the straight line connecting his eye to the object that is nothing but is the ‘Line of Vision’, beautiful. Let’s see, he is going to see a few more examples. What is he doing? Yeah, this time what is he seeing? He is seeing the beautiful flowers on the ground there. So now he is the observer and that flower is the object that straight line is nothing but again, you know, it is line of vision. Isn’t that easy?
Now Raj is going to do something more interesting, what is he doing? Yes, he is saying I want that apple, which apple, yes, that apple there on the tree. Now Raj is the observer and that apple is the object. So the straight line connecting his eye to that object is the ‘Line of Vision’. So this is what we say, so we understood what is Line of Vision, it is so very simple, wherever an observer observes an object, the line connecting his eye to the object is called Line of Vision. And that is the concept, isn’t that easy, the first concept we have learnt it, very simple.
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State Board English Std X Algebra Demo Videos
In this module we will be seeing a word problem based on speed, distance and time. A very interesting sum based on walking and cycling. Let us take up the question and the question is this Problem Set 2, 30th main question, sub question no.xx.
Let us read the question, from the same place at 7 am, ‘A’ started walking in the north at the speed of 5 kms per hour. After 1 hour ‘B’ started cycling in the east at the speed of 16 km per hour. At what time they will be at a distance of 52 kms apart from each other is the question, right. At what time means the question is about time. But before getting into what is to be found, you understand when we read the problem there was something called north and east. There are directions in the sum. So let us understand directions over here. Suppose this is a ground, north and east, north and east directions were mentioned in the sum. North and east are two perpendicular directions we understand, right. Now let us read the problem, part by part, step by step.
From the same place, suppose the place is this ‘O’, from the same place at 7 am, at what time, at 7 am, ‘A’ started walking in the north. ‘A’ started walking in which direction, north, means he went upwards, at a speed of 5 kms per hour. So what is the speed of ‘A’, 5 kms per hour, right.
Then what else is said, after one hour, ‘A’ started at 7 am, after one hour, after one hour means what time, after one hour means at 8 am, after one hour means at 8 am, ‘B’ started cycling in the east with a speed of 16 kms per hour. East means which direction, this direction, ‘B’ started cycling in the east, this direction. With a speed of how much, 16 kms per hour. So what is the speed of ‘B’, 16 kms per hour, right.
So let us understand this problem with the help of an animation. At 7 am ‘A’ started walking in the north, and at 8 am ‘B’ started cycling in the east. Question asked is at what time they will be at a distance of 52 kms apart from each other. So at what time the distance between ‘A’ and ‘B’ will become 52 kms is the question asked. Is the question clear, at what time? At 7 am ‘A’ started, at 8 am ‘B’ started. At what time they will be at a distance of 52 kms apart from each other is the question asked. At what time the distance between ‘A’ and ‘B’ will become 52 kms is the question asked.
So if you can see this is a right angled triangle. So let us draw the right angled triangle AOB, right. Now the speed of A is 5 kms per hour, the speed of B is 16 kms per hour. And the distance between A and B is 52 kms, this much we have understood.
Now let us tabulate this data whatever we know. First is A, next is B, now time, what time, what is the time taken by A and what is the time taken by B, let us find out that. At what time A started walking, A started walking at 7 am, right. And what time B started cycling. B started cycling at 8 am, right, we know this. The question is about time, the time one of them has to be x, and what is the other let us see. The question is about time. A started walking at 7 am and B started cycling at 8 am we know. And we also know that the distance between A and B at some time is 52 kms, right. The question asked to you is at what time the distance between A and B will become 52 kms. Suppose at 11 am, at 11 o’clock, A and B were at a distance of 52 kms apart from each other suppose, right. Now A started at what time, 7 o’clock and he reached point A at what time 11 am. B started at what time, 8 am, and he reached spot B at 11 am only, because at 11 o’clock they are at a distance of 52 kms apart from each other. So A started at 7 am and reached spot A at 11 am. B started at 8 am and reached spot B at 11 am. That means what we understand, we understand that A travelled one hour more than B, yes or no. Whatever time B travelled A travelled one more hour. If B travelled for 5 hours then A travelled for 6 hours, one hour more. That means if B travelled for x hours, A travelled for how many hours, x+1 hour. Now since we don’t know the time taken of A and B, we will assume let the time taken by B to reach spot B be x hours. So time taken by A will automatically be 1 hour more, because he travelled 1 hour more, it will be how much x+1 hour. So time is clear.
Next, we know the speed of A, what is the speed of A, 5 kms per hour. We know the speed of B also, how much is that, 16 kms per hour. Since we know time and we know speed, we can calculate distance. Distance is nothing but speed into time, distance is nothing but speed into time. So speed of A is 5 into the time taken by A is (x+1). So 5 into (x+1) so many kms. Similarly we can find out distance travelled by B also. Distance travelled by B will be nothing but again speed of B will be 16 kms per hour into time taken by B will be nothing but x hours. So 16 into x, 16x kms. Now since we know both these distances, distance covered by A and distance covered by B and also we know distance between A and B 52 kms. So let us put these distances in the place of distances, right. So all the three distances we know, we know OA, we know OB and as well as we know AB.
Now if we see this triangle, this triangle AOB is nothing but a right angled triangle. That means in this right angled triangle how to form an equation connecting all these three. We can use Pythagoras theorem.
In right angled triangle AOB Pythagoras theorem we can write
OA2 + OB2 = AB2. Let us put the values of OA, OB and AB.
OA2 means 5 into (x+1) the whole square + OB2 means 16 x the whole square is equal to AB2 which means 522.
Right, we got the equation, how to solve it we will see in the next module.
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