Class X, Light - Reflection and Refraction | CBSE Physics (Science) | NCERT Solutions (Exercise Questions)

CBSE Science - Physics

Class X, Light - Reflection and Refraction

NCERT solutions (Textbook Exercise Questions)  

Q.1: Which of the following materials can not be used to make a lens?

(a) water (b) glass (c) plastic (d) clay

Ans: (d)

Q.2: The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?

(a) between the principal focus and the center of curvature

(b) at the center of the curvature

(c) beyond the center of curvature

(d) between the pole of mirror and its principal focus.

Ans: (d)

Q.3: Where should an object be placed in front of convex lens to get a real image of the size of the object?

(a) at the principal focus of the lens

(b) at twice the focal length

(c) at infinity

(d) between the optical center of the lens and its principal focus.

Ans: (b)

Q.4: A spherical mirror and a thin spherical lens have each a focal length of –15 cm. The mirror and the lens are likely to be

(a) both are concave (b) both are convex (c) the mirror is concave and the lens is convex (d) the mirror is convex and but the lens is concave.   

Ans: (a)

Q.5: No matter how far you stand from a mirror, our image appears erect. The mirror is likely to be –

(a) plane only (b) concave only (c) convex only (d) either plane or convex.

Ans: (d)

Q.6: Which one of the following lenses would you prefer to use while reading small letters found in a dictionary?

(a) A convex lens of focal 50 cm (b) A concave lens of focal 50 cm

(c) A convex lens of focal length 5 cm (d) A concave lens of focal length 5 cm.  

Ans: (c)

Q.7: We wish to obtain an erect image of an object using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.

Ans: 

Range of the distance of the object = 0 to 15 cm from the pole of the mirror. 

Nature of the image = virtual, erect and larger than the object.

Q.8: Name the type of mirror used in the following situations –

(a) Head lights of a car (b) Side / rear-view mirror of vehicle (c) Solar furnace 

Support your answer with reason.

Ans: (a) Concave mirror, (b) Convex mirror, (c) Concave mirror.

Reason: Concave mirrors are convergent mirrors. They converge the light incident on them to a single point i.e. at the principal focus and produce a large amount of heat at that point.   

Q.9: One half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.

Ans: Yes, the lens will produce a complete image of the object although one half of a convex lens is covered with a black paper.

Experimental verification: A convex lens which is covered one half with a black paper is taken. Put an object before it and obtained an image on the screen by adjustment. There it can be observed that the lens produces the complete image of the object.

Explanation / Observation:

Case I: 

When the upper half of the lens is covered (as shown in the above figure) then rays of light incident from the object will be refracted by the lower half of the lens and meet at the other side of the lens to form a complete image of the object.

Case II:

When the lower half of the lens is covered then rays of light incident from the object will be refracted by the upper half of the lens and meet at the other side of the lens to form a complete image of the object (as shown in the above figure).

Q.10: An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.

Ans: 

h₁ = 5cm, u = –25cm, f = + 10cm

Q.11: A concave lens of focal length 15 cm form an image of 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.

Ans:  

Q.12: An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.

Ans: 

Q.13: The magnification produced by a plane mirror is +1. What does this mean?

Ans: The positive sign means image formed by a plane mirror is virtual and erect. Since the magnification is 1 it means that the size of the image is equal to the size of the object.  

Q.14: An object 5 cm is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position, nature and size of the image.

Ans: 

Q.16: Find the focal length of a lens of power –2.0 D. What type of lens is this?

Ans:

Q.17: A doctor has prescribed a corrective lens of power +1.5 D. Fined the focal length of the lens. Is the prescribed lens diverging or converging?

Ans: 

CBSE Class X NCERT Physics Chapter 10, Light - Reflection and Refraction

• NCERT (CBSE) Solutions Class 10 Science - Physics | Chapter 10 LIGHT - REFLECTION AND REFRACTION - Notes and Sample Questions |  Lesson 1 of 3

• Class 10th CBSE NCERT Science (Physics) Solutions | LIGHT - REFLECTION AND REFRACTION | In-Text Questions

• Class X, NCERT CBSE Science (Physics) | CCE type Multiple Choice Questions (MCQ) | Chapter 10, Light - Reflection and Refraction 

• CBSE Hot Questions - NCERT Science Questions Bank | Class X Physics (Science) | Light: Reflection and Refraction

Class IX CBSE (NCERT) English Communicative (Literature Reader) | Keeping It From Harold | CCE type Sample Questions - Answers

CBSE Class IX English Communicative

NCERT English Literature Reader

F4. Keeping It From Harold

CCE type Multiple Choice Questions (MCQ)

Read the following extract and answer the following questions by choosing the most appropriate alternative from the options given below:

Q.1: “Ma!” Mrs. Bramble looked up, beaming with a kind of amiable fat – headedness. A domestic creature, wrapped up in Bill, her husband and Harold, her son. At the present moment only the latter was with her.

(a) Who is referred to as a domestic creature?

(i) Mrs. Bramble (ii) Bill (iii) Harold (iv) Major Percy Stokes

(b) What does fat – headedness mean?

(i) Intelligence (ii) Wisdom (iii) Foolishness (iv) Indifference

(c) Who was sitting beside her at that moment?

(i) Bill (ii) Harold (iii) Major Stokes (iv) Mr. Fisher  

Q.2: A slight frown marred the smoothness of Harold Bramble’s brow. It jarred upon him, this habit of his mother’s referring to herself in the third person, as if she were addressing a baby, instead of young man of ten who had taken the spelling and dictation prize last term on his head.

(a) Why did Harold not like his mother’s habit of referring to herself in the third person?

(i) She treated him as if he were a baby. (ii) She treated him as if he were a stranger.

(iii) She treated him as if he were an adult (iv) She treated him as if he were her brother.

(b) How old was Harold?

(i) 7 years (ii) 8 years (iii) 9 years (iv) 10 years.

(c) Harold had taken the spelling and dictation prize. It shows that he        

(i) was good at games (ii) had high IQ (iii) was good at studies (iv) often won prizes.

Q.3: The spectacled child considered the point for a moment gravely. Then, nodding he arranged his books in readiness for his return and went out. The front door closed with a decorous softness.

(a) Harold was spectacled. It means he

(i) was good looking (ii) was ugly (iii) wore glasses (iv) had good eyesight.

(b) What suggestion of his mother did he agree to?

(i) Arranging his books (ii) Reading quietly (iii) Having a walk by the river (iv) Closing the door softly.

(c) Harold closed the door with a decorous softness. This indicates that he was –

(i) well-behaved and sensible (ii) rude and disobedient (iii) lazy and easy-going (iv) always in hurry.   

Q.4: The only drawback was that his very perfection had made necessary a series of evasions and even deliberate falsehoods on the part of herself and her husband, highly distasteful to both. They were lovers of truth, but they had realized that there are times when truth must be sacrificed.  

(a) What ‘perfection’ is referred to here?

(i)  Harold was very good at studies. (ii) Harold was a perfect sportsman.

(iii) Harold was a model of a son. (iv) Harold was devoted to his books and a model of behaviour.

(b) Harold’s parents

(i) always told lies (ii) always spoke the truth

(iii) were compelled to tell lies (iv) would not tell lies at any cost.

Q.5: A little later, when the child had begun to show signs of being about to become a model of goodness and intelligence, and had already taken two prizes at the Sunday-school, the senior curate of the Parish, meeting Mr. Bramble one morning, said nervously – for after all, it was a delicate subject to broach, “Er –Bramble, I think, on the whole, it would be as well to - er - keep it from Harold.

(a) How had Harold shown signs of becoming a model of goodness and intelligence?

(i) Won prize at dictation. (ii) Won two prizes at the Sunday-school.

(iii) Won a prize as the best student at school. (iv) Won a prize reciting poetry.

(b) What did the senior curate advise Mr. Bramble?

(i) To send Harold to a resident school. (ii) To send Harold to a Sunday-school regularly.

(iii) Not to tell Harold about his profession. (iv) Not to let Harold take part in wrestling.

(c) Why did the curate give that advice to Mr. Bramble?

(i) Mr. Bramble’s profession was illegal. (ii) Mr. Bramble’s profession was considered respectable.

(iii) Mr. Bramble’s profession was not considered respectable. (iv) Mr. Bramble was unemployed.        

CCE type Short Answer Questions

Q.6: What was extraordinary about Harold?

Q.7: When Percy and Bill came home, what strange news they give to Mr. Bramble?  

Q.8: What were Jerry Fisher’s feelings for Mr. Bramble when the latter told him that he would not fight any longer at any cost?   

Q.9: What did Brambles think they must hide from Harold? Who else were of the same opinion?

Q.10: What does the writer say about Mr. Bramble’s skill as a professional boxer?

Click here to see Answers

FURTHER STUDY

Keeping It From Harold | CBSE Class IX Interact in English Communicative (Literature Reader) - NCERT Exercise Solutions [Read]

Keeping It From Harold | CBSE Class IX Interact in English Communicative (Literature Reader) - NCERT Exercise Solutions

Class 9 NCERT (CBSE) English Literature Reader (Communicative)

Keeping It From Harold

(NCERT solutions for Text Book Exercise Questions)

Q.1: Before you read “Keeping It From Harold” the teacher will encourage you to answer or discuss the following:

(a) What are the different weight categories in Boxing?

(b) Have you ever heard the song whose lyrics go like … “He floats like a butterfly and stings like a bee”? Who does ‘he’ refer to? He is also known as “The Greatest” boxer of all time. What was his original name? How many times did he win the World Heavyweight Belt?

(c) Find out from your friend if he/she watches WWE and who is his/ser favourite wrestler. Also find out why he/she likes this wrestler.

(d) Discuss with your friend as to why these wrestlers have such a large fan following. Has the perception of people changed over the century with respect to those who fight in the ring?  

Ans:

(a) The different weight categories in Boxing are – 1. Heavy weight, 2. Light heavy weight, 3. Cruiser weight, 4. Super middle weight, 5. Middle weight, 6. Light middle weight, 7. Welter weight, 8. Light welter weight, 9. Light weight, 10. Super feather weight, 11. Feather weight, 12. Bantam weight, 13. Super bantam weight, 14. Fly weight, 15. Super fly weight, 16. Light fly weight, 17. Minimum weight.

(b) Yes. Here, ‘he’ refers to Mohammad Ali who is also known as “The Greatest Boxer” of all time. His original name is Casius Clay. He won World Heavyweight Belt three times.

(c) Yes, my friend Sanju watches WWE. His favourite wrestler is Beth Phoenix. His punching is stylish and entertaining.         

(d) Yes, the perception of the people has changed over the time with respect to those who fight in the ring. Now they are celebrities. They earn lot of money and fame. They have fans all over the world and people see them with great respect.

Q.3: Answer the following questions by choosing the correct option:

(a) Mrs. Bramble was a proud woman because __________.

(i) She was the wife of a famous boxer.

(ii) She had motivated her husband.

(iii) She was a good housewife.

(iv) She was the mother of child prodigy.

(b) “The very naming of Harold had caused a sacrifice on his part.” The writer’s tone here is _______.

(i) admiring

(ii) assertive

(iii) satirical

(iv) gentle

(c) Harold had defined the laws of heredity by ______.

(i) becoming a sportsman.

(ii) being good at academics.

(iii) being well-built and muscular.

(iv) respecting his parents.

(d) Harold felt that he was deprived of the respect that his classmates would give him as _________.

(i) they did not know his father was the famous boxer, ‘Young Porky’.

(ii) his hero, Jimmy Murphy had not won the wrestling match.

(iii) he had not got Phil Scott’s autograph.

(iv) Sid Simpson had lost the Lonsdale belt.  

Ans: (a) iv (b) i (c) ii (d) i  

Q.4: Answer the following questions:

(a) What was the strange about the manner is which Mrs. Bramble addressed her son? What did he feel about it?

(b) Why was it necessary to keep Harold’s father’s profession a secret from him?

(c) When Mr. Bramble came to know that he was to become a father what were some of the names he decided upon? Why?

(d) Describe Mr. Bramble as he has been described in the story.

(e) Why was Mr. Bramble upset when she came to hear that Bill had decided not to fight?

(f) Who was Jerry Fisher? What did he say to try to convince Bill to change his mind?

(g) How did Harold come to know that his father was a boxer?

(h) Why was Harold upset that his father had not told him about his true identity? Give two reasons.  

(i) Do you agree with Harold’s parents’ decision of hiding from him the fact that his father was a boxer? Why/Why not?    

Ans:

(a) Mrs. Bramble used to speak to her son as if he were a baby, and not a young man of ten. She referred to herself in the third person. He disliked this habit of his mother.

(b) Harold’s father was a professional boxer. And Harold was a scholarly child with a very gentle and sophisticated behaviour. Mr. Bramble and his wife considered that boxing was an inferior profession and it may become difficult for Harold to accept the image and qualities of his father as displayed by any professional boxer. Hence, they thought it was necessary to hide his father’s profession from him.

(c) When Mr. Bramble came to know that he was to become a father he decided that the child should be named John, if it was a boy after Mr. John Sullivan and if it was a girl, she should be named Marie, after Miss Marie Lloyd.

(d) Mr. Bramble was a professional boxer. Yet he was an amiable and a very gentle person. He was proud of being a professional boxer. There was no man weighing eight stone four in London whom he could not overcome.

(e) Mrs. Bramble did not like her husband’s profession which she kept aloof from Harold. But Mr. Bramble used to earn lot of money that helped them to give a good education to Harold as they desired. She was upset because if her husband did not fight Murphy, he was not going to get the money they needed to give Harold a good future.  

(f) Jerry Fisher was Bill’s trainer at White Hart. He had been preparing Bill for the fight with Murphy. When Bill decided not to fight with Murphy, he tried to convince Bill to change his mind. Fisher told him that if he did not fight he would lose a lot of money. The spectators would also be disappointed and the media would not rightly be kind of him. On the other hand, a win against Murphy would bring him not only money, but also a huge popularity.

(g) Just when Jerry was trying to convince Bill not to give up the idea of fighting, Harold came in. He wanted to know what they were talking about him. Here Jerry told him that his father was not a commercial agent but a fighting man, a professional boxer who was popularly known as ‘Young Porky’.

(h) Here are the two reasons why Harold became upset when he came to know that his father had not told him about his true identity:

(1) Harold was deeply interested in boxing. He had betted Dicky Sauders that Jimmy Murphy wouldn’t last ten rounds against Young Porky. If his father did not fight he was sure to lose the bet.

(2) He was also upset because his father had kept from him his true identity. Boys at school had nicknamed him ‘Goggles’. If they knew that he was the son of Young Porky, they would hold him in awe. By hiding his true identity, his father had deprived him of the pride and respect he would have got from his schoolmates.

(i) I agree with Harold’s parents’ decision of hiding from him the fact that his father was a boxer. They considered that a professional boxer was looked upon as a low-profile entertainer, and most of the people in the society did not respect a boxer. By hiding father’s true identity from their son was they wanted to save Harold from the agony of being called the son of a petty boxer or fighter. But they did not have idea that time had changed and boxers were the heroes of younger generation and enjoy fans around the world.            

FURTHER STUDY

Class IX CBSE (NCERT) English Communicative (Literature Reader) | Keeping it from Harold | CCE type Sample Questions - Answers [Read]

CBSE Science Class IX Chemistry | Structure of the Atom | NCERT Solutions of Chapter 4 Intext Questions

Chapter 4, Structure of the Atom  

CBSE Board Class 9, NCERT Science (Chemistry)

Solutions of Chapter Intext Questions   

Q.1: What are canal rays?

Q.2: If an atom contains one electron and one proton, will it carry any charge or not?

Q.3: On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.

Q.4: On the basis of Rutherford’s model of an atom, which subatomic particle is present in the nucleus of an atom?    

Q.5: Draw a sketch of Bohr’s Model of an atom with three shells.   

Q.7: What do you think would be the observation if the α-particle scattering experiment is carried out using a foil of a metal other than gold?

Q.8: Name the three sub-atomic particles of an atom.

Q.9: Helium atom has an atomic mass of 4u and two protons in its nucleus. How many neutrons does it have?

Q.10: Write the distribution of electrons in carbon and sodium atoms.

Q.11: If K and L shells of an atom are full, then what would be the total number of electrons in the atom? 

Q.12: How will you find the valency of chlorine, sulphur and magnesium?

Q.13: If the number of electrons in an atom is 8 and the number of protons are also 8, then (i) what is the atomic number of the atom? (ii) What is the charge on the atom?

Q.14: For the symbol H, D and T tabulate three subatomic particles found in each of them.

Q.15: Write the electronic configuration of any one pair of isotopes and isobars.  

Click here to get Answers     

Further Study   

Structure of the Atom | Chapter 4, CBSE Class 9 Science (Chemistry) NCERT Solutions of Textbook Exercise [Read]

Class 9, NCERT - CBSE Science (Chemistry) | Chapter 4, Structure of the Atom | Sample Questions and study Materials [Read]

Class IX, CBSE - NCERT Chemistry (Science) | Chapter 4, STRUCTURE OF THE ATOM | Multiple Choice Questions (MCQ) [Read]

Structure of the Atom | Chapter 4, CBSE Class 9 Science (Chemistry) NCERT Solutions of Textbook Exercise

Structure of the Atom  

Class IX, NCERT (CBSE) Science (Chemistry)

Chapter 4, Exercise Solved   

Q.1: Compare the properties of electrons, protons and neutrons.  

Ans:

Particle	Nature of charge	Mass	Location
Electron	Negative (–1) or (–1.6 x 10–19 C)	9 x 10–31 kg	Extra nuclear part distributed in different shell or orbits.
Proton	Positive (+1) or (+1.6 x 10–19 C)	1.672 x 10–27 kg (1 µ) (approx. 2000 times that of the electron)	Nucleus
Neutron	No charge	1.672 x 10–27 kg (1 µ) (mass is nearly equal; to the mass of a proton)	Nucleus

Q.2: What are the limitations of J.J. Thomson’s model of the atom?  

Ans: According to J.J. Thomson’s model of an atom, it consists of a positively charged sphere with neutrons embedded in it. However, it was later found that the positively charged particles reside at the center of the atom called the nucleus, and the electrons revolve around the nucleus.

Moreover, Thomson attributed that the mass of an atom due to electrons and protons are evenly spread throughout the atom. This is not in agreement with the observations of Rutherford who concluded that mass is concentrated in a very small space in the center of the atom later called nucleus.    

Q.3: What are the limitations of Rutherford’s model of atom?

Ans: According to Rutherford’s model of an atom, electrons revolve around the nucleus in fixed circular orbits. We know, any particle revolving in a circular orbit would experience acceleration. Due to this acceleration, the electrons revolving in circular orbits will lose energy in the form of radiation and finally fall into the nucleus. In such a case, atom would be highly unstable which is not true.   

Q.4: Describe Bohr’s model of atom.

Ans: Bohr’s model of Atom

According to Bohr’s theory:

(1) The atom consists of a small positively charged nucleus at its center.

(2) The whole mass of the atom is concentrated at the nucleus and the volume of the nucleus is much smaller than the volume of the atom.

(3) All the protons and neutrons of the atom are contained in the nucleus.

(4) Only certain orbits known as discrete orbits of electrons are allowed inside the atom.

(5) While revolving in these discrete orbits electrons do not radiate energy. These orbits or cells are represented by the letters K, L, M, N etc. or the numbers, n = 1, 2, 3, 4, . . as shown in the above figure.

Q.5: Compare all the proposed models of an atom given in this chapter.

Ans:

Thomson’s Model	Rutherford’s Model	Bohr’s Model
1. An atom consists of a positively charged sphere and the electrons are embedded in it. 2. The negative and positive charges are equal in magnitude. As a result the atom is electrically neutral.	1. An atom consists of a positively charged center in the atom called the nucleus. The mass of the atom is contributed mainly by the nucleus. 2. The size of the nucleus is very small as compared to the size of the atom. 3. The electrons revolve around the nucleus in well-defined orbits.	1. Bohr agreed with almost all points as said by Rutherford except regarding the revolution of electrons for which he added that there are only certain orbits known as discrete orbits inside the atom in which electrons revolve around the nucleus. 2. While revolving in its discrete orbits the electrons do not radiate energy.

Q.6: Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements.  

Ans: Following rules are followed to fill electrons in different energy levels.

1. If n gives the number of orbit or energy level, then 2n² gives the maximum number of electrons possible in a given orbit or energy level. Thus,

First orbit or K-shell will have 2 electrons,

Second orbit or L-shell will have 8 electrons,

Third orbit or M-shell will have 18 electrons.

2. If it is the outermost orbit, then it should have not more than 8 electrons.

3. There should be step-wise filling of electrons in different orbits, i.e., electrons are not accompanied in a given orbit if the earlier orbits or shells are incompletely filled.  

Q.7: Define valency by taking examples of silicon and oxygen.  

Ans: The valency of an element is the combining capacity of that element. The valency of an element is determined by the number of valence electrons present in the atom of that element.

If the number of valence electrons of the atom of an element is less than or equal to four, then the valency of that element is equal to the number of valence electrons. For example, the atom of silicon has four valence electrons and so, it has valency equal to four.

On the other hand, if the number of the number of valence electrons of the atom of an element is greater than 4, then the valency of that element is obtained by subtracting the number of valence electrons from 8. For example, the atom of oxygen has 6 valence electrons. and so, the valency of oxygen is (8 – 6) 2. Q.8: Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and (iv) Isobars. Give any two uses of isotopes.  

Ans:

Atomic Number is defined as the number of protons present in the nucleus of an atom. For example, there are 6 protons in carbon, so the atomic number of carbon is 6. All atoms are characterized by their atomic numbers.

Mass Number is defined as the sum of the total number of protons and neutrons present in the nucleus of an atom. For example, there are 6 protons and 6 neutrons in the nucleus of carbon, so its mass number is 12.

Isotopes are atoms of the same element thus having same atomic number but different mass number. For example, chlorine has two isotopes with atomic number 17 but mass numbers 35 and 37 represented by -  

          

Two Uses of Isotopes

(a) Isotope of cobalt (⁶⁰Co) is used in the treatment of cancer.

(b) Isotope of uranium (²³⁵U) is used as a fuel in nuclear reactors.   

Isobars are such atoms which have same mass number but different atomic numbers. Thus, isobars are different elements. For example, Ne has atomic number 10 and sodium has atomic number 11 but both of them have mass numbers as 22 represented by -

Q.9: Na⁺ has completely filled K and L shells. Explain.  

Ans: The atomic number of sodium is 11. So, neutral sodium atom has 11 electrons and its electronic configuration is 2, 8, 1. But Na⁺ has 10 electrons. Out of 10, K-shell contains 2 and L-shell 8 electrons respectively. Thus, Na⁺ has completely filled K and L shells.    

Q.10: If bromine atom is available in the form of, say, two isotopes ⁷⁹₃₅Br (49.7%) and ⁸¹₃₅Br (50.3%), calculate the average atomic mass of bromine atom.

Ans: Isotope of bromine with atomic mass 79 u = 49.7%

Contribution of ⁷⁹Br to atomic mass of bromine

Q.11: The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes ¹⁶₈X and ¹⁸₈X in the sample?

Ans: 

Q.12: If Z=3, what would be the valency of the element? Also name the element.

Ans: If Z=3, i.e., atomic number is 3. The element is lithium and has distribution of electrons as 2, 1.

And so, lithium has a valency of 1.

Q.13: Composition of the nuclei of two atomic species X and Y are given as under

                          X    Y

Protons      =     6    6

Neutrons    =     6     8

Give the mass numbers of X and Y. What is the relation between the two species?

Ans:

Mass number of X = 6 + 6 = 12

Mass number of Y = 6 + 8 = 14

Since X and Y both have atomic numbers as 6 but mass numbers are different, therefore, these are isotopes.  

Q.14: For the following statements, write T for True and F for False.

(a) JJ Thomson proposed that the nucleus of an atom contains only nucleons.

(b) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral.

(c) The mass of an electron is about 1/2000 times that of proton.

(d) An isotope of iodine is used for making tincture iodine, which is used as a medicine.

Ans: (a) F (b) F (c) T (d) T

Put tick (√) against correct choice and cross (X) against wrong choice in the following questions:    

Q.15: Rutherford’s alpha-particle scattering experiment was responsible for the discovery of

(a) Atomic Nucleus  (b) Electron  (c) Proton  (d) Neutron.

Ans: (a) √ (b) X (c) X (d) X

Q.16: Isotopes of an element have

(a) the same physical properties

(b) different chemical properties

(c) different number of neutrons

(d) different atomic numbers.

Ans: (a) X (b) X (c) √ (d) X

Q.17: Number of valence electrons in Cl^– ion is:

(a) 16  (b) 8  (c) 17  (d) 18

Ans: (a) X (b) √ (c) X (d) X

Q.18: Which one of the following is a correct electronic configuration of sodium?

(a) 2,8  (b) 8,2,1  (c) 2,1,8  (d) 2,8,1

Ans: (d)

Further Study   

CBSE Science Class IX Chemistry | Structure of the Atom | NCERT Solutions of Chapter 4 Intext Questions [Read]

Class 9, NCERT - CBSE Science (Chemistry) | Chapter 4, Structure of the Atom | Sample Questions and study Materials [Read]

Class IX, CBSE - NCERT Chemistry (Science) | Chapter 4, STRUCTURE OF THE ATOM | Multiple Choice Questions (MCQ) [Read]