CBSE Class 8 Science Exemplar Chapter 16 Light NCERT Solutions

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NCERT Solutions PDF Class 8 PDF

This chapter, 'Light,' from the CBSE Class 8 Science Exemplar, delves into the fundamental principles of light and vision. The NCERT Solutions provide clear explanations for multiple-choice questions and other problems related to how we see objects, the role of the eye's parts like the iris and retina, and the laws of reflection. Understanding these concepts is crucial for grasping optics and visual perception. These solutions are designed to help students clarify doubts, reinforce their learning, and prepare effectively for their examinations by offering step-by-step guidance and accurate answers.

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Quick info

BoardCBSE
ClassClass 8
SubjectScience Exemplar
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 16

Chapter summary

Chapter 16, 'Light,' in the CBSE Class 8 Science Exemplar focuses on the basic phenomena of light, including how we perceive objects and the structure of the human eye. The NCERT Solutions cover key concepts such as the function of the iris in controlling light entry and the principle of light reflection from surfaces. The exercises aim to solidify understanding of these optical principles, ensuring students can apply them to various scenarios.

Learning outcomes

  • Understand the function of the iris in controlling light entering the eye.
  • Explain the process by which we see non-luminous objects.
  • Apply the laws of reflection to determine the angle of incidence and reflection.
  • Identify the conditions under which a mirror is visible.

Topics covered

Paper topics

  • Parts of the eye
  • Iris function
  • Vision
  • Non-luminous objects
  • Reflection of light
  • Laws of reflection
  • Angle of incidence
  • Angle of reflection
  • Mirror visibility

Important topics

  • Function of the Iris
  • Principle of Seeing Objects
  • Laws of Reflection
  • Conditions for Mirror Visibility

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Questions and Solutions

Multiple Choice Questions

1. Part of the eye which controls the light entering is called

(a) iris

(b) cornea

(c) lens

(d) retina

Solution: The correct option is (a) iris. The iris is a muscular structure located behind the cornea. It functions by adjusting the size of the pupil, thereby regulating the amount of light that enters the eye and reaches the retina. This control is essential for clear vision in varying light conditions.

2. We can see a non-luminous object when light:

(a) emitted by the object falls on the eye.

(b) is reflected from the object towards our eye.

(c) completely passes through the object.

(d) gets completely absorbed by the object.

Solution: The correct option is (b) is reflected from the object towards our eye. Non-luminous objects do not produce their own light. We are able to see them because light from a source (like the sun or a lamp) strikes the object, reflects off its surface, and then travels to our eyes. The reflected light allows us to perceive the object.

3. Light is falling on surface S1, S2, S3 as shown in Fig.16.1.

Surfaces on which the angle of incidence is equal to the angle of reflection is/are

  1. S1 only
  2. S1 and S2 only
  3. S2 and S3
  4. all the three surfaces
Solution: The correct option is (d) all the three surfaces. The laws of reflection, which state that the angle of incidence is equal to the angle of reflection, are fundamental principles of optics and apply universally to any surface where light reflects. Therefore, regardless of whether the surfaces are smooth or rough, this law holds true for all three surfaces S1, S2, and S3 shown in the figure.

4. A tiny mirror M is fixed on a piece of cardboard placed on a table. The cardboard is illuminated by light from a bulb. The position of eye with respect to position of bulb is shown in Fig.16.2 as A, B, C and D. In which position will the mirror be visible?

(a) A

(b) B

(c) C

(d) D

Diagram showing a mirror on a table with a bulb and possible eye positions A, B, C, D.
Solution: The mirror will be visible from position (B). For the mirror to be visible, the light from the bulb must strike the mirror and then reflect towards the eye. Position (B) is situated such that the light rays from the bulb can hit the mirror and reflect into the eye, allowing the observer to see the mirror. In other positions, the reflected rays may not reach the eye, or the direct line of sight to the mirror might be obstructed or not aligned with the reflection path.

Common mistakes

  • Confusing the roles of different parts of the eye (e.g., iris vs. cornea).
  • Misunderstanding that reflection is necessary to see non-luminous objects.
  • Incorrectly applying the laws of reflection to different types of surfaces.

Revision tips

  • Review the diagrams carefully to understand light paths.
  • Focus on the definitions and functions of key terms like 'iris' and 'reflection'.
  • Practice identifying the correct position for visibility based on reflection principles.

Practice MCQs

Q1. Which part of the eye is responsible for regulating the amount of light that enters?

Q2. For a non-luminous object to be visible, light must:

Q3. According to the laws of reflection, what is always true for light hitting a surface?

Frequently asked questions

What is the primary function of the iris in the human eye?

The iris controls the amount of light entering the eye by adjusting the size of the pupil. It can constrict in bright light and dilate in dim light.

How do we see objects that do not emit their own light?

We see non-luminous objects when light from a source, like the sun or a bulb, reflects off the object's surface and then enters our eyes.

Are the laws of reflection applicable to all surfaces?

Yes, the laws of reflection, which state that the angle of incidence equals the angle of reflection, apply to all surfaces, whether smooth or rough.

What is the relationship between the angle of incidence and the angle of reflection?

The angle of incidence is always equal to the angle of reflection. Both angles are measured with respect to the normal (a line perpendicular to the surface at the point of incidence).

How can these NCERT Solutions help with exam preparation?

These solutions provide clear, rewritten explanations for each question, helping students understand the concepts thoroughly and reinforcing their knowledge for exams.

Important links

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