Grade 5 General Science Chapter 10 Class 1 The sun the moon light travels in a straight line

good morning students today we will be going to start with the new chapter that is chapter 10 the sun earth moon light and shadow in this chapter we will be going to study about our solar system properties of light and phenomenon known as eclipses first let's see what our solar system is the sun its planets and all the objects moving around them is collectively known as the solar system we have total of eight planets earlier there were nine planets but later the ninth planet pluto was considered as dwarf planet so currently we have eight planets in our solar system the sun is the center of the solar system and the eight planets include mercury venus earth mars jupiter saturn uranus and neptune so the sun its planets and all the objects moving around them is collectively known as the solar system and all the planets revolving around the sun follow path known as the orbit now let's learn about our star that is the sun sun is the star and is the center of our universe that is the sun lies at the center of the solar system and it produces heat and light for the entire universe the sunlight enables us to see objects during the day so the light produced by the sun the sunlight helps us to see objects during the daytime and the sun is 150 million kilometers away from the earth so sun is star and produces heat and light the sunlight produced by the sun enables us to see objects during the day time and it is that is the sun is 150 million kilometers away from the earth now let's get to know about our planet earth earth is this third planet from the sun which means earth lies at the third position from the sun when planets are arranged in their order and it is the only planet known to support life so earth is the third planet from the sun that supports life and it is terrestrial planet with an atmosphere atmosphere means blanket of air that's around earth so the earth is surrounded by blanket of air known as the atmosphere and earth is terrestrial planet with an atmosphere that supports life it has natural satellite known as the moon so moon is the natural satellite of the planet earth now let's see what moon is moon is the brightest object in the night sky so in night sky the brightest object that you can see is the moon and it is the earth's natural satellite and it does not have its own light which means moon does not produce its own light but it appears brighter because of the light that is reflected by the sun so moon does not have its own light but it appears bright because light from the sun falls on it it revolves around the earth and rotates on its own axis so the moon shows two kinds of movements that is revolving around the earth as well as rotating on its own axis so moon is the natural satellite of the planet earth and it revolves around the earth and it rotates on its own axis if you observe the night sky on regular basis for longer period of time we can observe different shapes for the moon so how is this possible as the moon revolves around the earth on some nights we will be able to see full bright side of the moon while at some nights only portion of the bright side of the moon is visible why is this as the moon revolves around the earth on some nights we are able to see the full bright side of the moon which means the moon appears as full complete disc but on some nights we see only portion of the bright side of the moon these changing shapes of the moon is referred to as the lunar faces which means the appearance of the moon in different shades is referred to as the lunar faces how is this possible it is because of the revolution of moon around the earth we are able to see the lunar faces because of the revolution of the moon around the earth so the moon that is the natural satellite of the earth shows two kinds of moments it revolves around the earth as well as it rotates on its own axis the revolution of moon around the earth enables us to see the lunar faces now let's see how light travels so once the light is produced it always travels in straight line until it hits surface what enables us to see an object we just learned that the light travels in straight line so when the sun produces the light it gets dispersed in different direction when it hits an object for example in this picture the light from the sun hits on this flower and from there it gets reflected back to the person's eyes this is the pathway which enables us to see an object so light from the sun hits an object and it then get reflected to the person's eye this is the pathway which enables us to see an object so we see an object only when light that falls on it gets reflected and it reaches our eyes so this is how we are able to see an object with the help of light and the property of light that enables us to see an object in this case is the rectilinear propagation of light that means the light always travels in straight line let me prove this with the help of an experiment in this experiment two cases are given in the first one the individual uses straight pipe why in the second case the individual uses bended pipe to see the candle light in the first case the light reaches the eye and the person is able to see the light of the candle through the straight pipe while in the second case the light gets blocked and the person is not able to see the light of the candle because the pipe is bended that means the pipe is not straight and since light travels in straight line the person is not able to see the light of the candle so this activity proves that light always travels in straight line and justifies the principle of light that is the rectilinear propagation of light so we learned that light always travels in straight line and it enables us to see objects now let's do an activity in page number 129 let me read the activity for you first in the following situation when boy looks through the holes in the two wooden pieces he sees only the flower and not the leaves why so in this situation the child is able to see the flower while he is unable to see the leaves you have to find out the reason behind this what you have to do is you have to use ruler and join the red dots and let me repeat you have to use the ruler to join and after you have done that you have to find out the reason why the boy sees only the flowers and not the leaves so what you have to do is using ruler you have to join the dots and so it becomes clear that forms straight line while does not form straight line now you have to find out the reason why the boy sees only the flowers and not the leaves from the figure it is very clear that the boy is able to see the flower because abcd is straight line and the flower lies at this part while in the second case abef does not form straight line and this is the reason why the child is not able to see the leaves this proves that light always travels in straight line now let's do another activity in the same page that is page number 129 there four fill in the blanks questions are given and you have to answer them what you have to do is you have to pause the video answer them and come back to the video so the first question we are able to see objects during the day because of dash the answer is sun we are able to see objects during the day because of sun the second question the moon appears bright because light from the dash falls on it the answer is sun the moon appears bright because light from the sun falls on it the third question we do not see the darsh bright side of the moon on all nights the answer is full we do not see the full bright side of the moon on all nights the last question light travels in dark line the answer is straight line light travels in straight line we have completed answering the question that was all about today's class and in today's class we learned about the solar system the sun the earth the moon lunar faces and the property of light that is light travels in straight line hope all the concepts were clear to you thank you and have nice day