Orthographic projection concept: If a plane surface is parallel to a given plane of projection, how does it appear in that view?

Introduction / Context:
This question checks a fundamental rule of orthographic projection used in engineering graphics and technical drawing. Understanding how a geometric plane appears relative to a projection plane (front, top, or side) is essential to produce accurate multiview drawings.

Given Data / Assumptions:

• We are working with principal orthographic views (front, top, side).
• The object contains a flat plane surface (a true geometric plane).
• The plane in question is parallel to one projection plane.

Concept / Approach:
In orthographic projection, appearance depends on orientation: (1) If a plane is parallel to a plane of projection, it projects as a surface in true size and true shape. (2) If a plane is perpendicular to a plane of projection, it collapses to a line (an edge) in that view. (3) If a plane is inclined (neither parallel nor perpendicular), it appears foreshortened. The statement in the original stem claimed it would appear “on edge as a straight line,” which is the condition for perpendicularity, not parallelism.

Step-by-Step Solution:

Verification / Alternative check:
Sketch a rectangle lying parallel to the front plane. Its front view shows the full rectangle (true size). Rotate the rectangle 90 degrees so it is perpendicular; the front view collapses to a line. The contrast confirms the rule.

Why Other Options Are Wrong:

• Incorrect: “it appears only as an edge” corresponds to perpendicular orientation, not parallel.
• “Depends on scale” is irrelevant; scale does not change orientation effects.
• “Vanishes to a point” applies to a line perpendicular, not a plane.
• “Must be hatched” is a sectioning convention, unrelated to visibility rules.

Common Pitfalls:
Confusing “parallel to view direction” with “parallel to view plane”; mixing up rules for planes vs. edges; assuming foreshortening occurs for parallel planes (it does not).

Final Answer:
Correct: it appears in true size and shape as a surface, not as an edge