Class: Junior Secondary School 3 (JSS 3 / JS3)
Term: Third Term
Week: 9
Age: 14 years
Duration: 45 minutes
Subject: Basic Science and Technology
Curriculum Theme: Basic Science
Previous Lesson: Perspective Drawing: Definition.
Topic: ORTHOGRAPHIC PROJECTION
Subject Matter: Definition, Types (1st and 3rd angle), Drawing of orthographic views of simple objects: Dimension technique.

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define orthographic projection.
State the two main types of orthographic projection.
Explain the differences between first angle and third angle projection.

Affective Domain:

Appreciate the importance of orthographic projection in technical communication.
Show interest in drawing and interpreting technical diagrams.
Value precision and accuracy in technical drawings.

Psychomotor Domain:

Sketch the orthographic views (front, top, and side) of simple objects.
Apply basic dimensioning techniques to orthographic drawings.
Draw the symbols for first angle and third angle projection.

Collaborate with peers to identify views of objects.
Share ideas on how to represent objects accurately.
Participate actively in class discussions about technical drawings.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum
State Unified Scheme of Work
Basic Science and Technology for Junior Secondary Schools Book 3
https://www.google.com/search?q=orthographic+projection+jss3+curriculum
https://www.youtube.com/results?search_query=orthographic+projection+for+jss3

Instructional Materials

The teacher will teach this lesson with the aid of:

Models of simple geometric objects (e.g., cubes, rectangular prisms, L-shaped blocks)
Whiteboard or chalkboard
Markers or chalk
Drawing instruments (ruler, set squares, protractor)
Charts showing examples of 1st and 3rd angle projection

Rationale for the Lesson

This lesson helps pupils understand how three-dimensional objects are represented in two-dimensional drawings. It enables them to communicate technical ideas clearly and accurately, which is important for future studies in engineering, architecture, and other technical fields.

Prerequisite/Previous Knowledge

Pupils are expected to have a basic understanding of geometric shapes, lines, angles, and the concept of viewing objects from different perspectives.

Lesson Content/Board Summary

ORTHOGRAPHIC PROJECTION

Definition of Orthographic Projection

Orthographic projection is a way of representing a three-dimensional object in two dimensions by showing different views (like front, top, and side) as if looking directly at each face. These views are drawn at right angles to each other.

Types of Orthographic Projection

There are two main types of orthographic projection:

First Angle Projection:
In first angle projection, the object is imagined to be in the first quadrant. The views are placed such that the front view is above the top view, and the left-hand side view is placed to the right of the front view. It is commonly used in Europe and Asia.

Symbol for First Angle Projection: (A truncated cone is drawn, with the larger circle on the right and the smaller circle on the left, and a horizontal line through the center of both circles extending to the right, indicating the viewing direction.)
Third Angle Projection:
In third angle projection, the object is imagined to be in the third quadrant. The views are placed such that the front view is below the top view, and the left-hand side view is placed to the left of the front view. It is commonly used in North America.

Symbol for Third Angle Projection: (A truncated cone is drawn, with the larger circle on the left and the smaller circle on the right, and a horizontal line through the center of both circles extending to the right, indicating the viewing direction.)

Drawing Orthographic Views of Simple Objects

To draw orthographic views, identify the front, top, and side views of the object. Each view shows only two dimensions (e.g., length and height for front view, length and width for top view). The views are projected perpendicularly onto planes.

Steps for Drawing Orthographic Views:

Step 1: Identify the most descriptive view as the Front View.
Step 2: Draw the Front View, showing its length and height.
Step 3: Project lines vertically upwards from the Front View to draw the Top View, showing its length and width.
Step 4: Project lines horizontally from the Front View to draw the Side View, showing its height and width. (The side view can be either left-hand or right-hand, depending on the projection method).
Step 5: Ensure all views align correctly, with corresponding features lining up.

Dimensioning Techniques

Dimensioning is the process of adding measurements to a technical drawing to show the size and location of features on an object. Proper dimensioning is essential for manufacturing or constructing the object.

Key Elements of Dimensioning:

Dimension Line: A thin line with arrowheads at each end, indicating the extent of the dimension.
Extension Line: Thin lines extending from the object features to the dimension line. They should not touch the object outline.
Leader Line: A line pointing from a note or dimension to the feature it refers to.
Dimension Numerals: The numerical value indicating the size, placed above the dimension line.
Arrowheads: Small, filled triangles at the ends of dimension lines.

General Rules for Dimensioning:

Place dimensions outside the object outline where possible.
Avoid duplicating dimensions.
Keep dimension lines clear of other lines.
Use appropriate units (e.g., mm).

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher introduces the topic by showing pupils a simple 3D object model (e.g., a matchbox) and asks them how they would draw it accurately on a flat paper to show all its sides. The teacher then explains that today’s lesson is about a special drawing method called orthographic projection.
Pupils’ Activity: Pupils observe the object and attempt to describe how they would draw it, sharing their prior knowledge.
Learning Point: Pupils are introduced to the concept of representing 3D objects in 2D and understand the relevance of the lesson.

Step 2: Definition of Orthographic Projection

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines orthographic projection in simple terms, emphasizing that it shows different views (front, top, side) of an object at right angles to each other. The teacher writes the definition on the board.
Pupils’ Activity: Pupils listen attentively, ask questions for clarification, and copy the definition into their notebooks.
Learning Point: Pupils understand the meaning of orthographic projection.

Step 3: Types of Orthographic Projection

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains the two main types: First Angle and Third Angle Projection, using charts or sketches to illustrate the different arrangements of views and their respective symbols. The teacher also explains where each type is commonly used.
Pupils’ Activity: Pupils observe the illustrations, identify the differences, and copy the names and symbols of the projection types.
Learning Point: Pupils can identify and differentiate between first angle and third angle projection.

Step 4: Drawing Orthographic Views of Simple Objects

Time: 12 minutes
Teaching Skill: Demonstration/Practice
Teacher’s Activity: The teacher takes a simple object model and demonstrates how to identify its front, top, and side views. The teacher then sketches these views on the board, showing how they align for both first and third angle projections. The teacher also introduces basic dimensioning techniques.
Pupils’ Activity: Pupils observe the demonstration carefully, identify the views on the model, and attempt to sketch the views and apply basic dimensions in their notebooks.
Learning Point: Pupils begin to apply the principles of orthographic projection to draw simple objects and understand dimensioning.

Step 5: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

What is orthographic projection?
State the two main types of orthographic projection.
Explain one key difference between first angle and third angle projection.
List two elements used in dimensioning a drawing.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 6 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the definition, types, and importance of orthographic projection and dimensioning. The teacher assigns homework for pupils to draw the orthographic views of a given simple object and apply dimensions.
Pupils’ Activity: Pupils listen to the summary, ask any remaining questions, and copy down the homework assignment.
Learning Point: Pupils consolidate their learning and prepare for further practice.

Lesson Keywords

Orthographic – A type of projection in technical drawing where parallel lines are used to represent objects.
Projection – The process of representing a three-dimensional object on a two-dimensional surface.
First Angle Projection – A method where the object is between the observer and the projection plane.
Third Angle Projection – A method where the projection plane is between the observer and the object.
Front View – The view showing the main features of an object.
Top View – The view of an object seen from directly above.
Side View – The view of an object seen from either the left or right side.
Dimensioning – The process of adding measurements to a technical drawing.

Differentiation

For pupils who grasp the concept quickly, the teacher can provide more complex objects to sketch or challenge them to explain the applications of orthographic projection in real-world scenarios. For pupils who are struggling, the teacher will provide additional one-on-one guidance, simplify the objects, and use more physical models for hands-on exploration.

Note for teachers using this lesson plan

Emphasize practical demonstration using physical models. Encourage pupils to use drawing instruments for accuracy, even in initial sketches. Pay close attention to the correct alignment of views and the neatness of dimensioning. Ensure pupils understand that orthographic projection is a fundamental skill in many technical fields.