Answers of the most important science questions for 10 class CBSE board 2020-21
Answers of the most important science questions for 10 class CBSE board exam 2020-21
For the CBSE exam Class 10 Science paper 2021 which is going to be held on 21st May, we have examined important questions from all sections of each chapter of the Science NCERT book. This selection of important questions gives you an idea about the structures of the ideal science question paper and tool for the fast and powerful inputs for the incoming board exam.
Answers to each type of question have been designed and given independently. A few questions dependent on the viable standards are likewise given here. Our subject specialists have outlined these questions subsequent to conveying an exhaustive investigation of the previous years’ examination papers and the most recent assessment design. Here you will discover the questions dependent on each chapter of the CBSE Class 10 Science textbook.
Science’s most important questions and answers for 10 class CBSE board exams 2020-21 are designed here in order to make your path of preparation of the board exam easy. All answers to the most important science questions for class 10 CBSE board are explained here by an expert teacher of science as per the CBSE norms so you can confidently study the answers of most important science questions for 10 class CBSE board exams 2020-21 without a doubt. Answers of the most important questions of science for class 10 CBSE board exams 2020-21 are from throughout the science NCERT textbook and from the last year’s question papers. The students are required to get excellent marks in the exam and our requirement is to satisfy ourselves by proving quality study material with magnificent inputs for their study, so it is well for the students to get the quality study material. We assure you to get additional knowledge on our website. If you like this set of answers to science’s most important questions for class 10 CBSE board then please don’t forget to make a comment and share it with your friends also. There are two options available for you to study science questions and answers either download the PDF of science questions and answers for CBSE class 10 or you can study it online.
The questions in this post of answers of science questions for class 10 CBSE board exam 2020-21 are based on the NCERT textbook and the questions which have been asked within the last 10 years of board exams. Most of the questions we have written here have been asked frequently in the CBSE board exams. The answers to each question are explained in such a way to increase your basic knowledge of science.
Answers of the most important science questions for 10 class CBSE board exam 2020-21
Q1. Why do birds fly back to their nest in the evening?
Ans. The rating of the eye consists of two types of photoreceptors, rods, and cones, rods sensitized during the dim light or at the night. Cons are sensitized when the intensity of light is more or during the day time. Birds go back to their nests because their eyes consist of cons only due to which birds are capable to see during the day time only.
Q2. Why do you take time to find an object when you enter in the dimly lighted room from outside in the sun?
Ans. There is a tiny hole at the center of eye which regulates incoming light into the eye, when we see the objects in the intense light, its size becomes smaller and when we see the things in dark or dim light its size increases, so when we enter in the dimly lighted room from outside in the sun, the iris take some time to expand its size,in this time we can’t see the clear vision of the room and thus we take time to find the object inside a room.
Q3. Why does a ray of light splits when passed from prism?
Ans. A ray of light is composed of 7 colors of different wavelengths when light ray enters a prism its medium is changed, the speed of all the colors changes as per their individual wavelengths, it is that’s why light ray splits when passed from the prism.
Q4. Why doesn’t the planet appear to be twinkling?
Ans. The planets are part of our solar system, they are very closed to us, they don’t look like a pinpoint from the earth like stars. A light beam falls from the planets to our eyes is less refracted compared with a light ray which falls to our eyes from the stars, It is that’s why planets don’t twinkle like the stars.
Q5. Why we can’t see things very close to our eyes?
Ans. Our eye has the capability to see the near and far object is called the accommodation power of the eye. For seeing the distant object there is no limit, as an example stars are too far still our eye can see them, but for seeing the near object there is the limit, this is 25 cm, it is known as the near point of the normal human eye. The crystalline lens of our eye is unable to decrease its focal length of less than 25 cm, so we can’t see things very close to our eye.
Q6. When we see any object through the hot air over the fire, it appears to be wavy, moving slightly. Explain.
Ans. When light ray enters from one medium to another medium it gets refracted, when we see the objects across the fire, the light ray travels from cooler air to hotter air then it is refracted and incident on our eye, since the varying temperature of the hotter air the image formed by our eyes fluctuates, it is that’s why the object appears to be wavy, moving slightly.
Q7. Why does the sky appear blue on a clear day?
Ans. When light rays from the sun enter the atmosphere of the earth, the smaller size of gas molecules scatter the smaller wavelength colors of the light, violet, indigo, blue and green, among these, the chief colors are blue and green which makes the sky colors, it is that’s why the sky appears blue on a clear day.
Q8. A star sometimes appears brighter and some other times fainter. What is this effect called? State the reason for this effect.
Ans. A star sometimes appears brighter and some other times fainter, it is known as the twinkling effect. The stars are very far from the earth when the light from them enters the earth’s atmosphere, it refracted and then reaches to our eyes .as a result of this a virtual image is formed. Since the temperature of the atmospheric layers changes through which refraction takes place, thus the density of the atmospheric layers changes which results in the fluctuation in the position of the star, it is that’s why sometimes a star appears brighter and some times fainter, this effect is known as twinkling.
Q9. A student cannot see a chart hanging on a wall placed at a distance of 3 m from him. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagrams for the (i) defect of vision and also (ii) for its correction.
(b) We see advertisements for eye donation on television or in newspapers. Write the importance of such an advertisement.
Ans. The student is suffering from myopia since it is the effect due to which a person can’t see the objects after a certain distance known as far point of myopia or nearsightedness. It can be corrected by applying spectacles made of a pair of concave lenses.
(b) It is a bitter truth of life that everybody has to die one day, so everybody should donate his eye before death, it will give a vision to those children and people who can’t see this beautiful world being as alive. It is a good motive to inform people and other younger generations to be aware of this welfare cause through the advertisement in newspapers and television, so as a human being it is important to aware of everybody socially and emotionally so that number of donated eyes could be increased to help the number of persons who are visionless.
Q10. Explain giving a reason why the sky appears blue to an observer from the surface of the earth? What will the color of the sky be for an astronaut staying in the international space station orbiting the earth? Justify your answer by giving a reason.
Ans. The gas molecules of the earth atmosphere scatter the sunlight since these molecules are infinitesimally small in size so these molecules are capable to scatter only the shorter wavelength colors of the light, violet, indigo, green and blue but our eyes are sensitive to see only the green and blue colors so the dual effect of both colors is that sky looks blue from the surface of the earth.
Q11. (a) List three common refractive defects of vision. Suggest the way of correcting these defects.
(b) About 45 lac people in developing countries are suffering from corneal blindness. About 30 lac children below the age of 12 years suffering from this defect can be cured by replacing the defective cornea with the cornea of a donated eye. How and why can students of your age involve themselves to create awareness about this fact among people?
Ans.(a). Click the link Myopia, Hypermetropia, and Presbyopia
(b)We are human beings so it is our responsibilities to help another human being and when we have means available to help others then why shouldn’t we do that, the second thing it is a sensational feeling that after the death the donor’s eye will become immortal, the students of our age group can exchange this feeling to the people because for the children maximum people are kind, so we can create awareness this through an emotional play in the school, the students can create such a group to communicate whole of the society by a door to door call.
Q12. Explain why a ray of light passing through the center of curvature of concave minor gets reflected along the same path.
Ans. When a light ray passes through the center of curvature of the mirror, for this incoming ray the principal axis can be drawn as a tangent on the mirror, the ray since originated from the center of curvature so the ray is perpendicular to the principal axis(tangent) and the normal is always perpendicular to the principal axis, therefore normal and incident ray coincide to each other, so the incident angle is zero, according to the rules of reflection the incident angle is equal to the reflected angle, therefore reflected angle is also zero means the path of the incident ray and reflected ray is same, it is that’s why a ray of light passing through the center of curvature of concave minor gets reflected along the same path, see the fig. normal, incident ray and reflected ray all are coinciding to one another.
Q13. What is the important function of the presence of ozone in the earth’s atmosphere?
Ans. The important function of ozone is to absorb UV rays and protect us from harmful effects of ultraviolet violet rays which may cause skin cancer to all organisms on the earth.
Q14. The dark reaction of photosynthesis does not need light. Do plants undergo dark reactions at night? Explain.
Ans. As the name dark reaction doesn’t mean that it occurs at night or in dark, it is the reaction occurs subsequently to the first part of the photosynthesis reaction which is needed light and chlorophyll, in this light depended reaction actually energy molecules(ATP and NADPH) are formed, then for the second part of photosynthesis light is not needed, in this reaction energy molecule and carbon dioxide synthesize carbohydrate, so without the first part second part of the reaction can’t be completed, but the individually dark reaction to occur light is not required but it never occurs at night since until the light depended reaction complete dark reaction can not occur.
Please continue your study, you will find the rest of other similar important questions from the links mentioned at the starting of the post.