---
title: "In a Young’s double-slit experiment, monochromatic red light and monochromatic violet light are successively directed through the same slit apparatus onto a distant screen. Students observe that the bright interference fringes produced by the red light are spaced farther apart than the bright fringes produced by the violet light. Which of the following statements provides the best physical explanation for this observation?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/123178/"
date_modified: "2026-09-28T11:57:51+00:00"
---

# In a Young’s double-slit experiment, monochromatic red light and monochromatic violet light are successively directed through the same slit apparatus onto a distant screen. Students observe that the bright interference fringes produced by the red light are spaced farther apart than the bright fringes produced by the violet light. Which of the following statements provides the best physical explanation for this observation?

In a Young's double-slit experiment, monochromatic red light and monochromatic violet light are successively directed through the same slit apparatus onto a distant screen. Students observe that the bright interference fringes produced by the red light are spaced farther apart than the bright fringes produced by the violet light. Which of the following statements provides the best physical explanation for this observation?

![A horizontal diagram showing a vertical barrier on the left containing two narrow slits separated by vertical distance d. A vertical viewing screen is situated on the right at a horizontal distance L from the barrier. A horizontal dashed centerline extends perpendicular from the midpoint between the slits to the center of the screen. Two dashed straight lines extend from the two slits to a single common point on the screen located at a vertical displacement y above the centerline. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790596671-IF29qo.jpg)

- **A.** Red light travels at a higher speed in air than violet light, which allows the wavefronts emerging from the two slits to spread outward at a greater rate and separate further before reaching the screen.
- **B.** Violet light has a higher frequency and thus oscillates more rapidly, which causes destructive interference to dominate across a broader angular range and compresses the bright fringes closer to the central axis.
- **C.** Because both colors travel at the same speed, the lower frequency of red light corresponds to a longer wavelength, requiring a larger angular separation to achieve the path length difference needed for constructive interference.
- **D.** Because violet light has a shorter wavelength, each wave crest occupies less spatial distance, requiring a greater geometric path length difference between the slit paths to achieve a full-cycle phase shift.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123178/*