Topic: How does light travel?

Supplementary material for use in lessons in the group of natural sciences (nature, biology, chemistry, geography, physics), additional classes, science clubs. It can serve as a resource for expanding knowledge, preparing students for science competitions.

Target group

Students of an elementary school (geography).

Core curriculum

Grade VIII

Specific requirements

IX. Optics. Pupil:
1) illustrates the straight line propagation of light in a homogeneous medium; explains the formation of shadow and penumbra;
2) describes the phenomenon of reflection from a flat surface and from a spherical surface;
3) describes the phenomenon of light scattering when reflected from a rough surface;

General aim of education

Students explain how light moves in a specific center.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• you explain the concept of visible light;

• you will discuss examples of experiments showing that light propagates in straight lines;

• you will describe the relationship between the propagation of light in straight lines and the formation of solar eclipses and lunar eclipses.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers;

• items needed to carry out experiments: a cardboard box, a laser pointer or a small LED torch, a small light bulb powered from the network - one set per group (the teacher can use other light sources if it finds that they are suitable for carrying out the proposed experiments).

Lesson plan overview

Before classes

• Students get acquainted with the content of the abstract. They prepare to work on the lesson in such a way to be able to summarize the material read in their own words and solve the tasks themselves.

Introduction

• The teacher gives the topic, the goals of the lesson in a language understandable for the student, and the criteria of success.

Realization

• The teacher introduces the concept of visible light and explains to the students that light spreads in centers in a straight line.

• The teacher divides the class into small groups (maximum five people). Each team receives a set consisting of:
  - cardboard box;
  - laser pointer or a small LED flashlight;
  - a small light bulb powered from the network. The instructor announces the experience. They ask the students to write down the research question and the hypothesis in the form provided in the abstract. Then the students perform the experiment, record their observations and conclusions. Volunteers present them on the class forum..

• The teacher initiates a discussion about evidence of straight propagation of light. The students cite evidence resulting from their experiences.

• The guide, using the illustrations in the abstract, discusses the formation of solar eclipses and lunar eclipses as phenomena that are the consequences of straight‑line propagation of light.

• Students carry out the interactive exercises checking the level of knowledge learned during the lesson. The teacher initiates a discussion during which the correct solutions for all the exercises performed by the students are discussed.

• Work of the whole class team. Students stand in a circle. The teacher encourages them to play: throws a ball or mascot to one of the students, saying the English word or notion learned in the lesson. The student gives the Polish equivalent, mentions another word in English and throws a ball or mascot to a friend or colleague.

Summary

• At the end of the lesson the teacher asks: If there was going to be a test on the material we have covered today, what questions do you think would you have to answer? If the students do not manage to name all the most important questions, the teacher may complement their suggestions.

Homework

• Develop a lap book containing issues learned during the lesson and bring your work to the next class.

• Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

How does light travel?

Light travels exclusively along a straight line in given medium, e.g. in vacuum, air or water. This rule also applies to sun rays. They propagate from the Sun in straight lines, reaching also this part of Earth which at given moment faces the Sun.

Similar to all planets, Earth is opaque. Hence, half of the Earth globe is nearly always illuminated by Sun rays and there is day on it, while the second half is in shadow, and there is night on it. Sometimes the Sun, the Moon and Earth are aligned in one line. At that time, the Moon casts shadow on Earth surface, and people in that area can observe solar eclipse.

When light meets an opaque object, shadow, i.e. space deprived of direct access to light rays, appears directly behind it. There is no complete darkness in the shadow, because some light can get there in the result of reflection and dispersion of light in the adjacent areas.

• Light travels along a straight line.

• Shadow is created behind opaque objects.

• After hitting of an opaque obstacle, light can be reflected or dispersed.