Computer practice question for SSC. Review the correct answer and explanation, then continue with related practice below.
Which of the following is an input device that utilises a light-sensitive detector to select objects on a display screen?
Correct Answerसही उत्तर
A. Light PenA. लाइट पेन
Explanationव्याख्या
The correct answer is Light Pen.
According to the source, a light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's cathode-ray-tube display.
The book states that it allows a user to point to displayed objects or draw directly on the screen in a way similar to a touchscreen, but with greater positional accuracy.
Therefore the complete source-supported revision chain is: Light Pen — Input Device — Light-sensitive Wand — used with CRT Display — Select
Point to Displayed Objects — can Draw on Screen — source compares it with a touchscreen and describes greater positional accuracy.
Bar Code Reader, OMR and MICR are distractors.
The question provides the definition itself, so the terms 'light-sensitive detector' and 'display screen' are important clues.
The source does not explain the mechanisms of barcode readers, OMR or MICR in this entry.
Therefore those devices have not been expanded beyond their option names.
It also does not discuss modern display compatibility or historical usage of light pens.
For exam preparation, students should directly associate a light-sensitive pointing device with Light Pen.
Quick revision: Light Pen = Light-sensitive Input Device for Selecting or Drawing on Display, especially in conjunction with CRT according to the source.
Therefore option (a), Light Pen, is correct.
सही उत्तर Light Pen है। स्रोत के अनुसार Light Pen एक computer input device है जो light-sensitive wand के form में होता है और computer के cathode-ray-tube display के साथ use किया जाता है। Book बताती है कि इसके द्वारा user display पर objects को point/select कर सकता है या screen पर draw कर सकता है। Source इसे touchscreen के समान functionality वाला बताती है, लेकिन greater positional accuracy का उल्लेख करती है। इसलिए complete source-supported revision chain है: Light Pen — Input Device — Light-sensitive Wand — CRT Display — Objects Select/Point करना — Screen पर Draw करना — Touchscreen जैसा लेकिन Source के अनुसार Greater Positional Accuracy। Bar Code Reader, OMR और MICR distractors हैं। Question में 'light-sensitive detector' और 'display screen' strong clues हैं। Source इस entry में Barcode Reader, OMR या MICR के working principles explain नहीं करती, इसलिए उन्हें outside details से expand नहीं किया गया है। Modern displays के साथ light pen compatibility या historical usage भी source नहीं देती। Exam preparation में direct association रखें: Light-sensitive pointing input device = Light Pen। Quick revision: Light Pen — Input Device — Light Sensitive — CRT — Select/Draw on Screen। इसलिए विकल्प (a), Light Pen, सही उत्तर है।
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