Consider the following phenomena : 1. Size of the sun at dusk 2. Colour of the sun at dawn 3. Moon being visible at dawn 4. Twinkle of stars in the sky 5. Polestar being visible in the sky Which of the above are optical illusions?

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Q: 64 (IAS/2013)
Consider the following phenomena :
1. Size of the sun at dusk
2. Colour of the sun at dawn
3. Moon being visible at dawn
4. Twinkle of stars in the sky
5. Polestar being visible in the sky
Which of the above are optical illusions?

question_subject: 

Science

question_exam: 

IAS

stats: 

0,95,42,21,17,95,4

keywords: 

{'optical illusions': [0, 0, 0, 1], 'following phenomena': [0, 0, 1, 2], 'dusk': [0, 0, 0, 1], 'sky': [2, 1, 7, 11], 'stars': [0, 0, 0, 1], 'twinkle': [0, 0, 0, 1], 'sun': [3, 0, 0, 6], 'polestar': [0, 0, 0, 2], 'colour': [11, 6, 13, 28], 'moon': [2, 0, 5, 2], 'dawn': [0, 0, 0, 1]}

the correct answer is:

1, 2, and 4.

1. Size of the sun at dusk: This is an optical illusion known as the "apparent size hypothesis." The sun appears larger near the horizon due to a perceptual effect known as the Ponzo illusion, where objects in the distance appear larger than objects of the same size but closer.

2. Colour of the sun at dawn: The color of the sun at dawn or sunset appears different due to the scattering of shorter-wavelength light by the Earth`s atmosphere, resulting in a reddish or orange hue. This is not an optical illusion.

4. Twinkle of stars in the sky: The twinkling of stars is an optical illusion caused by the Earth`s atmosphere. The turbulence in the atmosphere causes the light from stars to scatter and fluctuate, leading to the appearance of twinkling.

Therefore, the correct answer is: 1, 2, and 4.

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