CDS (II) 2018 · General Knowledge
A full General Knowledge paper in the UPSC CDS pattern: 120 questions in 2 hours, with a third of the question's marks deducted for every wrong answer. Physics, Chemistry, Biology, defence and security, History, Geography, Polity, Economy and current events.
120questions
100marks
2 hoursno calculator
45/61/14easy / medium / hard
Topics in this paper
General Knowledge · 120 questions
- Physics15
- Biology14
- Chemistry13
- Polity12
- Defence10
- Indian Geography9
- Indian Economy9
- World Geography7
- Current Affairs6
- Sports5
- Freedom Struggle5
- Ancient India4
- Medieval India3
- Misc2
Sample question from this paper
Physics: optics · medium
Consider the following statements:
1. Total internal reflection occurs when light travels from a denser to a rarer medium at an angle of incidence greater than the critical angle.
2. Optical fibres transmit signals using total internal reflection.
Which of the statements given above is/are correct?
1. Total internal reflection occurs when light travels from a denser to a rarer medium at an angle of incidence greater than the critical angle.
2. Optical fibres transmit signals using total internal reflection.
Which of the statements given above is/are correct?
- A. 1 only
- B. 2 only
- C. Both 1 and 2
- D. Neither 1 nor 2
Show answer and solution
Answer: C
Statement 1 correctly states the conditions for total internal reflection: the ray must pass from a denser to a rarer medium and strike the boundary beyond the critical angle. Statement 2 is also correct, since light inside the core of an optical fibre is repeatedly totally reflected from the core-cladding boundary. Hence both statements are correct; light going from rarer to denser medium can never undergo TIR.
Statement 1 correctly states the conditions for total internal reflection: the ray must pass from a denser to a rarer medium and strike the boundary beyond the critical angle. Statement 2 is also correct, since light inside the core of an optical fibre is repeatedly totally reflected from the core-cladding boundary. Hence both statements are correct; light going from rarer to denser medium can never undergo TIR.