Verniers — if the smallest division of a vernier scale is longer than the smallest division of the main (primary) scale, what type of vernier is it? Select the correct name.

Introduction / Context:
Vernier scales enable readings finer than the main scale divisions by comparing slightly different pitches. The naming depends on whether the vernier divisions are shorter or longer than those of the main scale and on the direction in which the vernier graduations are laid out.

Given Data / Assumptions:

• Main scale division length is taken as the reference.
• Vernier’s smallest division is longer than the main scale’s smallest division.
• Least count is the absolute difference between one main division and one vernier division.

Concept / Approach:
When each vernier division is longer than one main division, the vernier must be laid out in the opposite (backward) direction to maintain readability. This configuration is termed a retrograde vernier. In contrast, a direct vernier has vernier divisions shorter than the main scale division and is laid out in the same direction.

Step-by-Step Solution:

Verification / Alternative check:
Instrument manuals distinguish direct and retrograde verniers exactly by this longer/shorter criterion and orientation.

Why Other Options Are Wrong:

• Direct vernier: V < M and same direction.
• Double vernier: Refers to two verniers for eliminating errors, not division length.
• Simple vernier: Generic term; not specific to V > M.

Common Pitfalls:
Confusing least count sign; remember least count is magnitude, not algebraic sign, and layout dictates the name.

Final Answer:
Retrograde vernier