ECAT Physics — Optical Instruments
Optical Instruments is part of the Physics section of the UET ECAT (30 of the 100 MCQs). It breaks into 4 subtopics, and we hold 21 ECAT-pattern practice MCQs on it, each with a written explanation. Tap a subtopic below to practise just that.
Subtopics (4)
How Optical Instruments is tested
Across the 7 ECAT past papers on ParhaiKrlo, Optical Instruments accounts for 5 questions. It appears in 5 of them, about 1 questions a paper. The heaviest was ECAT Past Paper 07, with 1 question.
| Paper | Questions |
|---|---|
| ECAT Past Paper 07 | 1 |
| ECAT Past Paper 05 | 1 |
| ECAT Past Paper 03 | 1 |
| ECAT Past Paper 02 | 1 |
| ECAT Past Paper 01 | 1 |
Optical Instruments MCQs from the ECAT past papers
Try each one before opening the answer. Each comes with a short explanation.
- Q1 · ECAT Past Paper 07 · Optical Instruments
When an optical fibre is used for data transmission, the angle of incidence of the light inside the fibre should be:
- A.Less than the critical angle
- B.Greater than the critical angle
- C.Less than the angle of refraction
- D.Greater than the angle of refraction
Show answer
Answer: B. Greater than the critical angle — Total internal reflection needs an angle of incidence greater than the critical angle.
- Q2 · ECAT Past Paper 05 · Optical Instruments
When an optical fibre is used for data transmission, the angle of incidence of the light inside the glass fibre should be:
- A.Less than the critical angle
- B.Less than the angle of refraction
- C.Greater than the critical angle
- D.Greater than the angle of refraction
Show answer
Answer: C. Greater than the critical angle — Light is guided by total internal reflection, which needs an angle of incidence greater than the critical angle.
- Q3 · ECAT Past Paper 03 · Optical Instruments
In a multimode graded-index fibre, the periphery, compared to the central core, has a:
- A.Higher refractive index
- B.Same refractive index
- C.Lower refractive index
- D.Similar refractive index
Show answer
Answer: C. Lower refractive index — In a graded-index fibre the refractive index is highest at the axis and falls gradually towards the edge.