ICSE Class 7 Physics, Unit 4: Light Energy
From the CISCE curriculum. 13 key concepts, about 5 days of study at 20 to 30 minutes a day.
What this unit aims at
Light travels in a straight line. Light from an object can move through space and reach the human eye which enables one to see this page, or a face in a mirror. This process is known as reflection. It obeys a law known as law of reflection. Light travels in air at a constant speed of 3 x 108 m/s or 3 lakh kilometre per second. In other mediums, like glass or water, it slows down. Light from sun is composed of seven colours. The colours of objects fascinates everybody, Physicists have found that all colours can be explained as addition of three primary colours. The primary colours are red, green and blue. Colours that is seen on a TV or computer screen arise due to combination of these primary colours. Appearance of colour of an object is due to process of absorption and reflection of different colours by the object.
Your child should be able to
- explain the phenomenon of reflection
- define the terms, plane, normal to the plane, point of incidence, angle of incidence and angle of reflection
- state the law of reflection
- describe reflection of light from a plane mirror
- use law of reflection to show formation of image by a plane mirror
- describe the characteristics of image formed by a plane mirror
- state the value of speed of light
- state primary colours
- describe formation of secondary colours by addition of primary colours
- explain the observed colour of an object based on reflection and absorption of light of different colours from the object
Key concepts in this unit
- Reflection:
- Definition and Examples.
- Terms related to reflection - normal, plane, point of incidence, angle of incidence, angle of reflection.
- Laws of Reflection.
- Plane mirror:
- Uses.
- Ray Diagram (no mention of virtual image). Characteristics of the image formed (Lateral
- Inversion, same size, distance is preserved).
- Speed of light (3 x 108 m/s).
- Primary colours (RGB).
- Formation of secondary colours by colour addition.
- Appearance of colour of an object (based on reflection and absorption)
- Colour subtraction.
Teach this unit at home
- A day-by-day plan from the CISCE concepts, so you know what to cover each day.
- A step-by-step script for each day, so you know what to say and ask (AI-written from the CISCE curriculum, so check it against your child's school book).
- A quiz at the end.
From the CISCE Curriculum for Classes I to VIII (2016). CISCE sets what is taught, not the textbooks, so schools use different books and there are no page numbers here. Adhian Gurus is not affiliated with CISCE.