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NCERT Solutions for Class 8 Science Chapter 16 Light

NCERT Solutions for Class 8 Science Chapter 16 Light

Edited By Vishal kumar | Updated on Sep 16, 2023 09:10 AM IST

NCERT Solutions for Class 8 Science Chapter 16 – Access and Download Free PDF

NCERT Solutions for Class 8 Science Chapter 16 Light are an essential part of the Class 8 NCERT curriculum. With these NCERT Solutions, achieving good marks in exams becomes an attainable reality. Let's consider a scenario: you're admiring your reflection in the mirror, but suddenly, the lights go out. In complete darkness, can you see your own face? The answer is no. This simple example highlights the crucial role of light in our ability to see.

CBSE NCERT solutions for Class 8 Science Chapter 16, "Light," not only help you assess your understanding of the chapter but also delve into the fascinating world of how light enables vision. Whether it's emitted or reflected by an object, light is the fundamental requirement for visualization. In this NCERT Class 8 Science chapter 16 Light , you'll explore the laws of reflection, which explain how light interacts with surfaces to allow us to see objects. The NCERT Science Chapter 16 solutions provide clear explanations for questions based on these reflection laws.

For a Class 8 student, CBSE NCERT solutions for Class 8 Science Chapter 16 Light serve as a valuable tool for completing homework assignments and performing well in exams. By understanding the principles of light and reflection presented in this chapter, you'll not only excel in your studies but also gain a deeper appreciation for the role of light in our daily lives.

**As per the CBSE Syllabus for the academic year 2023-24, this chapter has undergone a renumbering and is now designated as Chapter 12.

Free download class 8 science chapter 16 question answer PDF for CBSE exam

NCERT Solutions for Class 8 Science Chapter 16 Light

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NCERT Solutions for Class 8 Science Chapter 16 Light: Solved Exercise Questions

Q1. Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.

Answer:

No, we cannot see the objects inside the room but we might see the objects outside the room. An object is visible to us when light reaches it, gets reflected and reaches our eyes. Inside the darkroom there is no light present to be reflected from the objects and reach our eyes and therefore we won't be able to see them but if there is light present outside the room and if it is reflected from objects outside the room and if this light reaches our eyes then we would be able to see the objects outside the room.

Q2. Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?

Answer:

In regular reflection, the reflected rays are parallel to each other whereas in diffused reflection the reflected rays are not parallel to each other. In diffused reflection, the laws of reflection are not violated. In the case of diffused reflection, the surface from which reflection takes place has microscopical irregularities which means the surfaces at the points where each ray gets reflected from are not parallel to each other.

Q3. Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.

(a) Polished wooden table

Answer:

Regular reflection since the polished wooden table has a smooth surface.

Q3 (d). Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.

Marble floor with water spread over it

Answer:

Regular reflection since marble with water spread over it is a smooth surface.

Q4. State the laws of reflection.

Answer:

The laws of reflection are:

(i) The angle of reflection is always equal to the angle of incidence.

(ii) The incident ray, the reflected ray and the normal at the point of incidence to the surface on which reflection takes place all lie in the same plane.

Q5. Describe an activity to show that the incident ray, the reflected ray and the normal at the point of incidence lie in the same plane.

Answer:

Place a plane mirror on the table. Take a piece of paper and make a small hole in it. Ensure that the light in the room is dim. Hold the sheet normal to the table. Take another piece of paper and place it on the table in contact with the mirror. Draw a normal from the mirror on the paper kept on the table Now, light a torch on the mirror through the small hole such that the ray of light falls on the normal at the bottom of the mirror. When the ray from this hole is incident on the mirror, it gets reflected in a certain direction. You can easily observe the incident ray, reflected ray and the normal to the mirror at the point of incidence on the sheet placed on the table. This shows that the incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane.

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Q6. Fill in the blanks in the following.

(a) A person 1 m in front of a plane mirror seems to be _______________ m away from his image.
(b) If you touch your ____________ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with ____________.
(c) The size of the pupil becomes ____________ when you see in dim light.
(d) Night birds have ____________ cones than rods in their eyes.

Answer:

(a) A person 1 m in front of a plane mirror seems to be 2 m away from his image.
(b) If you touch your left ear with the right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with the left hand .
(c) The size of the pupil becomes large when you see in dim light.
(d) Night birds have fewer cones than rods in their eyes.

Choose the correct option in Question 7

Q7. Angle of incidence is equal to the angle of reflection.

(a) Always (b) Sometimes (c) Under special conditions (d) Never

Answer:

The angle of incidence is always equal to the angle of reflection. This is the first law of reflection, therefore, option (a) is correct.

Choose the correct option in Question 8

Q8. Image formed by a plane mirror is

(a) virtual, behind the mirror and enlarged.
(b) virtual, behind the mirror and of the same size as the object.
(c) real at the surface of the mirror and enlarged.
(d) real, behind the mirror and of the same size as the object.

Answer:

The image formed by a plane mirror is virtual, behind the mirror and of the same size as the object . Therefore option (b) is correct.

Q9. Describe the construction of a kaleidoscope.

Answer:

To make a kaleidoscope, get three rectangular mirror strips each about 15 cm long and 4 cm wide. Join them together to form a prism as shown in Fig. (a). Fix this arrangement of mirrors in a circular cardboard tube or tube of a thick chart paper. Make sure that the tube is slightly longer than the mirror strips. Close one end of the tube by a cardboard disc having a hole in the centre, through which you can see [Fig (b)]. To make the disc durable, paste a piece of the transparent plastic sheet under the cardboard disc. At the other end, touching the mirrors, fix a circular plane glass plate [Fig (c)]. Place on this glass plate several small pieces of coloured glass (broken pieces of coloured bangles). Close this end of the tube by a ground glass plate. Allow enough space for the colour pieces to move around.

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Q10. Draw a labelled sketch of the human eye.

Answer:

1659590635585The human eye consists of retinae, lens, cornea, optic nerve, iris, ciliary muscle

Q11. Gurmit wanted to perform Activity 16.8 using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teacher’s advice?

Answer:

Laser light can harm the eye if looked at directly because of its high intensity and therefore Gurmit's teacher advised her to not use it.

Q12. Explain how you can take care of your eyes.

Answer:

We can take care of our eyes by following the following steps:

(i) Keeping a distance of at least 25 cm between our eyes and a book while reading it.

(ii) Not looking at a laptop or TV screen for a long time.

(iii) Regularly cleaning our eyes.

(iv) Visiting an ophthalmologist regularly.

Q13. What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray?

Answer:

The angle of incidence = angle of reflection. since the angle between the incident and reflected ray is 90 degrees. the angle of incidents will be 90/2 =45 degrees

\\Angle \ of \ incidence \ = \ Angle \ of \ reflection \\Angle \ of \ incidence \ + \ Angle \ of \ reflection \ = \ 90\degree \\ 2 \times Angle \ of \ incidence \ = \ 90\degree \\ Angle \ of \ incidence \ = \ 90\degree\div \2 \\ Angle \ of \ incidence \ = \45\degree

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Q14. How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?

Answer:

An infinite number of images of the candle will be formed because when an object is placed between to parallel plane mirrors an infinite number of images are formed.

Q15. Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in Fig. 16.19. Draw the reflected ray from the second mirror.

1659590751655

Answer:

We use the first law of reflection to draw the path of the ray. It states the angle of incidence is equal to the angle of reflection.

1659590768280

Q16. Boojho stands at A just on the side of a plane mirror as shown in Fig. 16.20. Can he see himself in the mirror? Also, can he see the image of objects situated at P, Q and R?

light16

Answer:

Boojho cannot see himself in the mirror because of the short length of the mirror. He would be able to see objects at position P and Q but not at R.

Q17. (a) Find out the position of the image of an object situated at A in the plane mirror (Fig. 16.21).

(b) Can Paheli at B see this image?
(c) Can Boojho at C see this image?
(d) When Paheli moves from B to C, where does the image of A move?

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Answer:

(a) The image of object A forms behind the mirror at a distance equal from the mirror equal to the distance between the object and the mirror.

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(b) Yes. Paheli at B can see this image.

(c) Yes. Boojho at C can see this image.

(d) Image of the object at A will not move. It will remain in the same position when Paheli moves from B to C.

Subject matter experts from Careers360 have created a comprehensive class 8 science chapter 16 question answe, presented in easy-to-understand language and step-by-step. The solution includes a total of seventeen questions, consisting of MCQs, fill-in-the-blanks, and short answer types. Students can also download the class 8 chapter 16 science solution and use it as a reference to reinforce their understanding of the chapter. In addition, the solutions have been curated keeping in mind the latest curriculum and are aimed at helping students score well in their exams.

NCERT Solutions For Class 8 Science- Chapter-Wise

Class 8 Science Chapter 16 NCERT Solutions: Important Formulas and Diagrams

Laws of Reflection

Reflection is the process in which light, sound, or any other wave bounces back after striking a surface. When light or sound waves encounter a surface, they can't pass through it, so they bounce off. This bouncing back of waves is called reflection.

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The law of reflection states that when a light ray or any other wave encounters a reflecting surface, the angle at which it strikes the surface (angle of incidence) will be equal to the angle at which it bounces off (angle of reflection). Both the incident and reflected rays, along with the normal line perpendicular to the surface, lie within the same plane. This law applies universally to all reflective surfaces.

Image formation in a plane mirror

In a plane mirror, the image formed is virtual, erect, and laterally inverted, appearing at the same distance as the object, with the angle of incidence equal to the angle of reflection.


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Number of Images(n)

n= (360o/θ)-1

Human Eye


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NCERT Solutions for Class 8 Science Chapter 16 Light: Points to Remember

  • All surfaces reflect light.
  • Reflection can be regular and diffused, depending on whether the surface is smooth or rough.
  • Regular reflection takes place through smooth surfaces whereas diffused reflection occurs through rough surfaces.
  • Questions on this concept are explained in NCERT solutions for Class 8 Science Chapter 16 Light
  • There are two laws of reflection which can be stated as-

(i) The angle of incidence is equal to the angle of reflection.

(ii) The incident ray reflected ray and the normal drawn at the point of incidence to the reflecting surface, lie in the same plane. The details of the terms used will be studied in NCERT solutions for Class 8 Science chapter 16 Light.

  • When two mirrors are combined at particular angles, they give multiple images.
  • Kaleidoscope is one of the applications of multiple reflections that help in making beautiful patterns. Question number 9 in the NCERT solutions for Class 8 Science chapter 16 Light explains the construction of kaleidoscope.
  • The plane mirror forms laterally inverted images
  • Braille system helps visually impaired persons to read

NCERT chapter 16 Light also explains the structure of the eye and its functioning. It also deals with how we can take care of our eyes. Question 10 in the NCERT Solutions for Class 8 Science chapter 16 Light shows a labelled structure of the human eye.

Light Class 8 Science Chapter 16-Topics

Topics for science chapter 16 class 8 are given below:

  • What makes Things Visible
  • Laws of Reflection
  • Regular and Diffused Reflection
  • Reflected Light Can be Reflected Again
  • Multiple Images
  • Sunlight — White or Coloured
  • What is inside Our Eyes?
  • Care of the Eyes
  • Visually Challenged Persons Can Read and Write
  • What is the Braille System?

Key Features of Light Class 8 Questions and Answers

  1. Comprehensive Coverage: Theselight class 8 ncert solutions cover all the important topics related to "Light" in the Class 8 curriculum.

  2. Concept Clarity: The class 8 science chapter 16 question answer provides clear and concise explanations to ensure students understand the concepts thoroughly.

  3. Variety of Questions: The questions cover a range of topics, including laws of reflection, the behaviour of light, and practical applications.

  4. Practice Questions: Multiple practice class 8 science chapter 16 ncert solutions help students reinforce their understanding and problem-solving skills.

  5. Visual Aids: Diagrams and illustrations are included in class 8 light ncert solutions where relevant to enhance understanding.

  6. Real-Life Examples: The light class 8 questions and answers often include real-life scenarios to help students relate to the concepts.

  7. Free Access: These class 8 science ch 16 question answer are freely accessible, making them available to all students for study and revision.

These features make science chapter 16 class 8 "Light" Questions and Answers a valuable resource for students, facilitating their understanding of the subject and preparation for exams.

Also Check NCERT Books and NCERT Syllabus here:

NCERT Solutions For Class 8: Subject-Wise

Frequently Asked Question (FAQs)

1. What is light?

Light is the smallest quantity of energy that can be transported  a photon an elementary particle without a real size that can be split, only created or destroyed    

2. What are the topics covered in NCERT Class 8 Science chapter 16 Light?

Here are the topics covered in NCERT Class 8 Science chapter 16 Light 

  • What makes Things Visible
  • Laws of Reflection
  • Regular and Diffused Reflection
  • Reflected Light Can be Reflected Again
  • Multiple Images
  • Sunlight — White or Coloured
  • What is inside Our Eyes?
  • Care of the Eyes
  • Visually Challenged Persons Can Read and Write
  • What is the Braille System? 
3. How many questions in NCERT Class 8 Science chapter 16 Light?

There are 17 questions in NCERT Class 8 Science chapter 16 Light

4. What is reflection?

Reflection is when a wave hits a boundary and bounces back in the opposite direction with the same frequency, wavelength, and speed. The angle of incidence equals the angle of reflection.

5. What are the benefits of using the NCERT Solutions for Class 8 Science Chapter 16?

The benefits of using NCERT Solutions for Class 8 Science Chapter 16 include accurate and easy-to-understand answers, step-by-step solutions, and improvement in problem-solving skills. These solutions are helpful for exam preparation and save students' time and effort.

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A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

Option 1)

0.34\; J

Option 2)

0.16\; J

Option 3)

1.00\; J

Option 4)

0.67\; J

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times.  Assume that the potential energy lost each time he lowers the mass is dissipated.  How much fat will he use up considering the work done only when the weight is lifted up ?  Fat supplies 3.8×107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate.  Take g = 9.8 ms−2 :

Option 1)

2.45×10−3 kg

Option 2)

 6.45×10−3 kg

Option 3)

 9.89×10−3 kg

Option 4)

12.89×10−3 kg

 

An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1)

2,000 \; J - 5,000\; J

Option 2)

200 \, \, J - 500 \, \, J

Option 3)

2\times 10^{5}J-3\times 10^{5}J

Option 4)

20,000 \, \, J - 50,000 \, \, J

A particle is projected at 600   to the horizontal with a kinetic energy K. The kinetic energy at the highest point

Option 1)

K/2\,

Option 2)

\; K\;

Option 3)

zero\;

Option 4)

K/4

In the reaction,

2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}

Option 1)

11.2\, L\, H_{2(g)}  at STP  is produced for every mole HCL_{(aq)}  consumed

Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

Option 3)

33.6 L\, H_{2(g)} is produced regardless of temperature and pressure for every mole Al that reacts

Option 4)

67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, Mg_{3}(PO_{4})_{2} will contain 0.25 mole of oxygen atoms?

Option 1)

0.02

Option 2)

3.125 × 10-2

Option 3)

1.25 × 10-2

Option 4)

2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1)

decrease twice

Option 2)

increase two fold

Option 3)

remain unchanged

Option 4)

be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1)

Molality

Option 2)

Weight fraction of solute

Option 3)

Fraction of solute present in water

Option 4)

Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol-1) is

Option 1)

twice that in 60 g carbon

Option 2)

6.023 × 1022

Option 3)

half that in 8 g He

Option 4)

558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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