CBSE Class 7 Science Revision Notes Chapter 15

CBSE Class 7 Science Revision Notes Chapter 15 – Light

Life on earth would have never been possible without light. Over the decades, scientists delved into the nature of light and discovered much more about it. The CBSE Syllabus introduces students to the concept of light in Class 7 Chapter 15 “Light, Shadow, and Reflection”. The chapter explains how light rays are emitted, how they travel, and what properties they show while travelling from one place to another. To make the chapter easier, Extramarks provides Class 7 Science Chapter 15 Notes prepared by subject matter experts.

These notes are meticulously designed as per the revised CBSE guidelines. Conceptual clarity is very important to answer all the questions in the exam hall. Therefore, students can utilise these notes in which concepts are explained in simple language. Real-life examples and illustrations are given for easier learning. Students can make the most of these notes and revise effectively before the exams.

Revision Notes For CBSE Class 7 Science Chapter 15
Access Class 7 Science Chapter 15 – Light Notes

CBSE Class 7 Science Chapter 15 Light Notes
Light: Class 7 Science Chapter 15 Revision Notes Summary

  • Light is a form of energy that travels in a straight line. Unlike sound waves, light rays can pass even if there is no medium to travel through. But there are certain objects that do not let light rays pass through them. These objects are called opaque objects. Based on the ability of the light rays to pass through, there are other kinds of objects known as transparent objects and translucent objects. 
  • Students can utilise these Class 7 Science Chapter 15 Notes to clear their doubts regarding the chapter. These concepts are illustrated with suitable examples which makes it easier for students to relate the concepts to their daily life. These notes are well-structured, which will help them understand the flow from one concept to another.
  • The notes describe how different conditions influence the behaviour of light rays. When light rays fall on a smooth and polished surface they bounce back. The phenomenon of the light rays bouncing back is known as reflection. When we see ourselves in a mirror, it is a result of this reflection. This reflection follows a set of laws known as the laws of reflection. These laws are also stated and explained with examples. Students can refer to this section of the notes for further clarification.
  • The notes then proceed further to introduce different types of lenses. The concave lens curves inwards, whereas the convex lens curves outwards. The topic of different images formed through these lenses is important from the exam perspective. Convex lens refers to the scientific term for a magnifying glass. Students will learn the various applications of concave and convex lenses.
  • Students will also learn the concepts of visibility range and range of lateral inversion in plane mirrors. If one stands in front of a long mirror, their left hand seems their right in the reflection. Students can understand this phenomenon once they gain conceptual clarity about the mentioned topics. Class 7 Science Chapter 15 Notes will help every student grasp every topic so that they face no difficulty when studying them in advanced classes.
  • Moving on to the next section, students will learn that light is made of colored light rays. Though light itself is not visible, it makes everything visible by reflecting on it. They are visible when they fall on the surface of the prism. The breaking of white light into seven different colours is known as the dispersion effect. Violet, indigo, blue, green, yellow, orange, and red (VIBGYOR) are the seven colours that together make white light.
  • In this section, students will learn the three properties of light: rectilinear propagation of light, light reflection, and dispersion. The property of rectilinear propagation allows light to move in a straight line in any direction thus moving on in the form of rays. Reflection of light is a phenomenon that is elaborated on in the previous sections. Here, students have to memorise important terms like the angle of incident, normal, and angle of reflection which are extremely crucial for understanding the behaviour of light. Dispersion, in a nutshell, is the breaking of white light into the lights of seven colours.
  • After going through the notes, students will be able to answer all of the critical questions such as the differences among the images made by different lenses, the properties shown by light, and the laws of reflection, which are slightly advanced concepts. Extramarks offers subject-matter expert-written revision notes in crisp and easy-to-understand language for simple understanding. Students can access these notes and improve their command of the chapter on light.

FAQs (Frequently Asked Questions)

1. How does light reflect on a shiny surface?

When light rays pass from one medium to another, some allow the light rays to pass while others do not. However, light rays fall on certain objects which reflect the light rays in different directions. This event of the light rays bouncing off after falling on a medium is called reflection. The smoother the surface is, the greater the amount of light that gets reflected. This reflection also depends on the angle of incidence and the surface of the medium.

2. What is the difference between reflection and refraction?

Reflection is the phenomenon when light rays return to the first medium after falling on the second medium by changing their direction. Refraction is the phenomenon when light rays do not come back and pass through the second medium but change their direction. Refraction can be best observed when light rays fall on the surface of a lens.

3. What is the dispersion effect of light?

The dispersion effect of light refers to the phenomenon of the splitting of white into seven different lights. The sunlight apparently seems white in colour, but in reality, it consists of seven colours, namely, violet, indigo, blue, green, orange and red. These colours are not normally visible. But when sunlight falls on the surface of a CD, soap bubbles, or on the glass surface of a prism, the seven colours can be distinguished individually.

4. What kind of lens is used in a magnifying glass?

The images formed with convex lenses are larger than the real objects. So, a convex lens is a right choice for making a magnifying glass.