---
title: "Time to display a pixel"
subject: "Computer Graphics"
chapter: 1
key: "semester_5/computer_graphics:time-to-display-pixel"
source: https://www.bctengineer.com/q/semester_5/computer_graphics/time-to-display-pixel
site: BCT Engineering
---

# Time to display a pixel

Computer Graphics · Chapter 1: Introduction and Application

- Asked in: 2082 Kartik (new course), 3 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/computer_graphics/time-to-display-pixel
- Whole chapter: https://www.bctengineer.com/md/semester_5/computer_graphics/chapter-1

## Question

Calculate the time required to display a pixel on the monitor of size 1024 × 768 with refresh rate of 60 Hz.

## Short answer

Total pixels per second = 1024×768×60 = 47,185,920. Time to display one pixel = 1 / 47,185,920 ≈ 21.2 ns.

## Answer

The screen is refreshed 60 times per second, and each refresh must access all pixels.

```text
Pixels per frame = 1024 × 768 = 786,432
Pixels per second = 786,432 × 60 = 47,185,920
Time per pixel = 1 / 47,185,920 s
               = 2.119 × 10⁻⁸ s ≈ 21.2 ns
```

**Answer: about 21.2 ns per pixel** (retrace time ignored).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How many pixels does 1024 x 768 have?
   A. 78,643
   B. 1,792
   C. 7,864,320
   D. 786,432
   Answer: D. 1024 x 768 = 786,432. (Key point: Pixels per frame)

2. How many pixels are accessed per second at 60 Hz?
   A. 47,185,920
   B. 786,432
   C. 4,718,592
   D. 60,000
   Answer: A. 786,432 x 60. (Key point: Pixels per second)

3. What is the time per pixel?
   A. About 21.2 us
   B. About 21.2 ns
   C. About 16.7 ms
   D. About 2.12 ns
   Answer: B. 1 / 47,185,920 = 2.119 x 10^-8 s. (Key point: Time per pixel)

## Related in Computer Graphics

- [Pixel access rate of raster system](https://www.bctengineer.com/question.md?key=semester_5%2Fcomputer_graphics%3Apixels-per-second-access-time) — Computer Graphics, chapter 1
- [Frame buffer size for 1 min video](https://www.bctengineer.com/question.md?key=semester_5%2Fcomputer_graphics%3Aframe-buffer-1min-video) — Computer Graphics, chapter 1, asked 2×
- [Time to scan one row of pixels](https://www.bctengineer.com/question.md?key=semester_5%2Fcomputer_graphics%3Arow-scan-time-refresh) — Computer Graphics, chapter 1
- [Raster display and frame buffer load time](https://www.bctengineer.com/question.md?key=semester_5%2Fcomputer_graphics%3Araster-system-load-time) — Computer Graphics, chapter 1
- [Memory for 10 minute SVGA video](https://www.bctengineer.com/question.md?key=semester_5%2Fcomputer_graphics%3Aframe-buffer-svga-10min) — Computer Graphics, chapter 1, asked 2×

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