Atmospheric Refraction (Twinkling of Stars, Apparent Position of Sun) MCQs

Q1. Consider the following statements about atmospheric refraction: (I) Stars twinkle due to atmospheric refraction. (II) The Sun appears flattened at the horizon. (III) Planets twinkle more than stars. Which of the above statement(s) is/are correct?

• A.Only III
• B.Only I and II
• C.Only I
• D.None of these

Answer: B. Only I and II

Textbook fact: Correct: I, II. Applying this to the choices: Correct. The other choices: option A) 'Only III' doesn't hold - Re-check each statement individually; option C) 'Only I' is incorrect: Re-check each statement individually; option D) 'None of these' misses the point - Re-check each statement individually. So the correct option is B) Only I and II.

Q2. An astronomy club times both sunrise and sunset and finds that atmospheric refraction makes the Sun appear to rise 2 minutes early; by symmetry it also delays sunset by the same amount. By how many minutes is the total length of daylight increased, as written in the club bulletin?

• A.0 minutes
• B.4 minutes
• C.1 minutes
• D.2 minutes

Answer: B. 4 minutes

Refraction advances sunrise by 2 min and delays sunset by an equal 2 min. Both ADD to the daytime, so extra daylight = 2 + 2 = 4 min.

Q3. A weather station measures the length of the day and finds that atmospheric refraction makes the Sun appear to rise 2.2 minutes early; by symmetry it also delays sunset by the same amount. By how many minutes is the total length of daylight increased, as written in the meteorology sheet?

• A.1.1 minutes
• B.0 minutes
• C.4.4 minutes
• D.2.2 minutes

Answer: C. 4.4 minutes

Refraction advances sunrise by 2.2 min and delays sunset by an equal 2.2 min. Both ADD to the daytime, so extra daylight = 2.2 + 2.2 = 4.4 min.