Energy, Power and Intensity of Light - High School Physics

This post shares a physic's lesson dealing with the notions of Energy, Power and Intensity of light. It comes as a set of 6 videos (all included in this post).

Last Monday, the lesson of the Openschool had to start later than usual. As a consequence, some of the students had to leave the classroom before the end of the lesson in order to go to their after-school jobs (In Nigeria, many high school students have to do so to help their families). 

So I made a series of videos summarizing what we had seen during the first part of the class and developing further the last part for the students that missed it. I often do this especially if the Internet connection is a little rough, and then send the videos to their teacher @obamike so that they can review them in class. 

I reformatted the videos a little and posted them on the brand new Openschool Youtube channel (Follow us on YT!).

The aim of this lesson is to briefly remind the concepts of Energy and Power and then introduce the notion of light Intensity. The level is around first year / second year High school (Grade 10-11).  

Part 1: Energy and Power

A brief reminder of the definitions of Energy and Power (this topic has been already discussed extensively with the students in previous lessons), but I always make a point to remind them of these crucial notions.  

Part 2: Notion of Light Intensity

Introduction of the concept of light Intensity by using the example of a planar source of light. Followed by an exercise

 

Want to give a shot at the exercise? 

Part 3: Light Intensity - Exercise.

A more advanced exercise about light intensity in relation with the World cup! In addition a reminder on how to handle multiple of units following a question that occurred during the live lesson.  

 

Part 4: Intensity provided by a punctual source of light

This video shows how a punctual source of light spreads its power on a spherical surface. It also discusses some basic quantitative geometry concerning circles, disks and spheres.  

Part 5: Light Intensity from a punctual source of light - Exercise.

This video presents an exercise involving energy, power and intensity of punctual sources of light. I noticed many students encounter trouble when entering numbers with powers of ten in their calculator: Tips are given on how to handle these numbers effectively, thus reducing the risk of error.  

Want to give a shot at the exercise first?  

Part 6: Exercise - Calculating the solar constant of Earth and Mars

The Light intensity received at the level of a planet orbiting the sun is called the Solar Constant. In this exercise, I ask the students to calculate the Solar Constant of Earth and Mars. 

 

Want to give it a try first?  

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• Presentation video:

 

 All visual elements in this post and the videos originate from Pixabay.com or were created by @muphy.

Except for the football pitch (source) And the close picture of the sun (source)

The background music in the videos was produced by @muphy