Question 33 GLI03 - Master-LT 500-1600 GRT

The Correct Answer is B **Explanation for Option B (67.5°):** Option B (67.5°) is correct because it aligns with the specifications for the stern light (or "after masthead light" if applicable, though typically referred to simply as the stern light) as defined in the International Regulations for Preventing Collisions at Sea (COLREGs) and generally mirrored in inland rules. Rule 21 defines the characteristics of navigation lights: * A **Stern light** is a white light placed as nearly as practicable at the stern showing an unbroken light over an arc of the horizon of **135 degrees** and so fixed as to show the light **67.5 degrees** from right aft on each side of the vessel. * $67.5^{\circ} \text{ (starboard side)} + 67.5^{\circ} \text{ (port side)} = 135^{\circ} \text{ total arc}$. The question specifically asks how many degrees the light shows on **each side of the stern**, which is 67.5 degrees. **Explanation of Why Other Options Are Incorrect:** * **A) 22.5°:** This is the angle of overlap between the sidelights (red and green) and the masthead light(s). It is not the angle of the stern light on one side. * **C) 112.5°:** This is the arc of visibility for the sidelights (port light/red light and starboard light/green light). Each sidelight shows from dead ahead to 112.5 degrees aft on its respective side. It is not the arc for the stern light on one side. * **D) 135.0°:** This is the **total arc** of visibility for the stern light (i.e., $67.5^{\circ} + 67.5^{\circ}$). It is not the angle shown on *each side* of the stern.